Hong Kong (CNN) Hong Kong's leader invoked rarely-used emergency powers to ban people from wearing face masks during public assemblies, a move that enraged thousands of protesters who marched through streets across the territory on Friday night.

The city's major transport network MTR suspended all of its operations after demonstrators vandalized a number of areas within Hong Kong -- from train stations to shopping malls and banks.

The mask ban comes into effect on October 5, Chief Executive Carrie Lam announced at a press conference Friday, following a special meeting of her cabinet, the Executive Council.

The embattled leader said the order to enact the "Prohibition On Face Covering Regulation" was a "necessary decision" but insisted it does not mean Hong Kong was in a state of emergency.

"We are now in a rather extensive and serious public danger. It is essential for us to stop violence and restore calm to society as soon as possible," she said. "We believe the new law will create a deterrent effect against masked protesters and rioters."

Lam said she won't set a date to nullify the anti-mask law.

The vast majority of people who have attended the city's recent pro-democracy demonstrations do so wearing masks to hide their identity , fearful that they could be arrested or targeted by police. Gas masks and respirators to protect against tear gas, which is often used by authorities to disperse unauthorized gatherings, have also become commonplace.

In order to enact such a ban the Chief Executive Office will invoke the city's colonial-era Emergency Regulations Ordinance, which grants the government sweeping emergency powers.

Photos: Hong Kong unrest A riot policeman sprays pepper spray at a man as they disperse a crowd during a demonstration against "parallel traders" who buy goods in Hong Kong to resell in mainland China on Sunday, January 5. Hide Caption 1 of 160 Photos: Hong Kong unrest Pro-democracy supporters hold placards as they take part in a New Year's Day rally on Wednesday, January 1 in Hong Kong. Hide Caption 2 of 160 Photos: Hong Kong unrest Pro-democracy supporters wave flags during a countdown party in Tsim Sha Tsui district on New Year's Eve. Hide Caption 3 of 160 Photos: Hong Kong unrest Police arrive to conduct a clearance operation in the Kowloon district of Hong Kong on December 31. Hide Caption 4 of 160 Photos: Hong Kong unrest Protesters take photos of a 'Free HK' light display at a gathering in the Central district of Hong Kong on December 30. Hide Caption 5 of 160 Photos: Hong Kong unrest A man is detained by riot police during a demonstration in a shopping mall at Sheung Shui district on December 28. Hide Caption 6 of 160 Photos: Hong Kong unrest A protester reacts after police fire tear gas to disperse bystanders in the Jordan district of Hong Kong, early on December 25. Hide Caption 7 of 160 Photos: Hong Kong unrest People celebrating the holidays react to tear gas as police confront protesters on Christmas Eve. Hide Caption 8 of 160 Photos: Hong Kong unrest Protesters march in Hong Kong. Hide Caption 9 of 160 Photos: Hong Kong unrest Protesters stage a rally outside the US Consulate in Hong Kong on Sunday, December 1. Hundreds gathered Sunday afternoon outside the US Consulate for another pro-US rally to show support for President Trump after he signed the Hong Kong Human Rights and Democracy Act into law. Hide Caption 10 of 160 Photos: Hong Kong unrest People take part in a march from Tsim Sha Tsui to Hung Hom in Hong Kong on December 1. Hide Caption 11 of 160 Photos: Hong Kong unrest Pro-democracy candidate Jimmy Sham, right, celebrates with a supporter after winning his election in the Sha Tin district, early November 25. "Today's result represents (my constituency's) support to protesters. The government should immediately establish the Five Demands and respond to the public's voices," Sham posted on Facebook, referencing a long-standing protest slogan. Hide Caption 12 of 160 Photos: Hong Kong unrest Pro-democracy candidate James Yu hugs his girlfriend after winning his seat in district council elections, early November 25. Hide Caption 13 of 160 Photos: Hong Kong unrest People line up to vote outside of a polling place in Hong Kong, November 24. More than 2.9 million people turned out to vote in Sunday's elections, which have been framed as a de facto referendum on the almost six months of ongoing protests. Hide Caption 14 of 160 Photos: Hong Kong unrest Hong Kong Chief Executive Carrie Lam casts her ballot for the district council elections at a polling place, November 24. In a statement Monday, Lam said her government "respects the election results." Hide Caption 15 of 160 Photos: Hong Kong unrest A group of protesters leave the Hong Kong Polytechnic University holding hands before surrendering to police in the Hung Hom district on November 22. Hide Caption 16 of 160 Photos: Hong Kong unrest Protesters use clothes and helmets to form "SOS" at Hong Kong Polytechnic University on November 21. Hide Caption 17 of 160 Photos: Hong Kong unrest Protesters raise their hands to represent the five demands of pro-democracy demonstrators during a rally in support of the Hong Kong Human Rights and Democracy Act in the U.S., at the IFC Mall in Hong Kong, on November 21. Hide Caption 18 of 160 Photos: Hong Kong unrest Tables and chairs piled up to create a barrier are left behind by protesters who barricaded themselves inside the Hong Kong Polytechnic University. Hide Caption 19 of 160 Photos: Hong Kong unrest A Fire Services Department rescue diver prepares to enter the sewage system on November 20 to search for protesters who escaped from the Hong Kong Polytechnic University. Hide Caption 20 of 160 Photos: Hong Kong unrest Police detain a group of people after they tried to flee the Hong Kong Polytechnic University campus on November 19. Last week, thousands of student protesters streamed into the university and occupied the campus as the city's violent political unrest reached fever pitch. Hide Caption 21 of 160 Photos: Hong Kong unrest A protester uses a flashlight while crawling through a sewer tunnel to see how wide it is as he and others try to find an escape route from the Hong Kong Polytechnic University on November 19. Hide Caption 22 of 160 Photos: Hong Kong unrest A protester walks through a gymnasium at Hong Kong Polytechnic University on November 19. Hide Caption 23 of 160 Photos: Hong Kong unrest Protesters react as police fire tear gas in the Kowloon area of Hong Kong, Monday, November 18. Hide Caption 24 of 160 Photos: Hong Kong unrest Firefighters put out a burning car set on fire by protesters near Hong Kong Polytechnic University in the Tsim Sha Tsui district on November 18. Hide Caption 25 of 160 Photos: Hong Kong unrest Police in riot gear move through a cloud of smoke as they detain a protester at the Hong Kong Polytechnic University in Hong Kong on November 18. Police have attempted to clear the university , which has been occupied by protesters for days as a strategic protest base. Hide Caption 26 of 160 Photos: Hong Kong unrest Police fire tear gas as protesters attempt to leave Hong Kong Polytechnic University via a bridge on November 18. Hide Caption 27 of 160 Photos: Hong Kong unrest A member of the police clashes with a protester at the Hong Kong Poytechnic University on November 18. Hide Caption 28 of 160 Photos: Hong Kong unrest Protesters use a rope to lower themselves from a pedestrian bridge to waiting motorbikes to escape from police at Hong Kong Polytechnic University on November 18. Hide Caption 29 of 160 Photos: Hong Kong unrest A protester throws an umbrella onto a fire at the barricaded main entrance of Hong Kong Polytechnic University on November 18. Hide Caption 30 of 160 Photos: Hong Kong unrest An anti-government protester is detained at Hong Kong Polytechnic University on November 18. Hide Caption 31 of 160 Photos: Hong Kong unrest An anti-government protester is showered down by volunteer medical workers after he was soaked by a police water cannons firing pepper spray-infused water at Hong Kong Polytechnic University on November 18. Hide Caption 32 of 160 Photos: Hong Kong unrest Riot police fire tear gas and rubber bullets as protesters attempt to leave Hong Kong Poytechnic University on November 18. Hide Caption 33 of 160 Photos: Hong Kong unrest A protester prepares to shoot an arrow during a confrontation with police. Hide Caption 34 of 160 Photos: Hong Kong unrest Police use a water cannon outside the Hong Kong Polytechnic University. Hide Caption 35 of 160 Photos: Hong Kong unrest A protester throws a Molotov cocktail at police on November 17. Hide Caption 36 of 160 Photos: Hong Kong unrest Protesters use a catapult to fire bricks at the police from inside the Hong Kong Polytechnic University on November 17. Hide Caption 37 of 160 Photos: Hong Kong unrest A woman tries to hold back riot police from approaching the Hong Kong University in Hong Kong on Saturday. Hide Caption 38 of 160 Photos: Hong Kong unrest Protesters train to throw Molotov cocktails into a swimming pool on the campus of the Hong Kong Polytechnic University on November 14. Hide Caption 39 of 160 Photos: Hong Kong unrest Protesters walk past barricades of bricks on a road near the Hong Kong Polytechnic University on November 14. Hide Caption 40 of 160 Photos: Hong Kong unrest Demonstrators gather during a lunchtime protest in the financial district of Hong Kong on November 14. Hide Caption 41 of 160 Photos: Hong Kong unrest A protester releases a flaming arrow to light a barricade at The Chinese University of Hong Kong (CUHK), Wednesday, November 13. Hide Caption 42 of 160 Photos: Hong Kong unrest A Molotov cocktail, a gas mask and a yellow construction helmet are placed upon a bust of late hotel tycoon Hui Yeung Shing at the campus of The Chinese University of Hong Kong on November 13. Hide Caption 43 of 160 Photos: Hong Kong unrest A fire is seen at a Mass Transit Railway (MTR) station during a demonstration at The Chinese University of Hong Kong on November 13. Hide Caption 44 of 160 Photos: Hong Kong unrest Students attempt to clear tear gas canisters fired by riot police onto a sports track during a confrontation at the Chinese University in Hong Kong on Tuesday, November 12. Hide Caption 45 of 160 Photos: Hong Kong unrest A man is detained during a protest at the Chinese University of Hong Kong on November 12. Hide Caption 46 of 160 Photos: Hong Kong unrest Students block an escalator with chairs in an attempt to hamper police at the University of Hong Kong on November 12. Hide Caption 47 of 160 Photos: Hong Kong unrest A protester is detained in the Central District of Hong Kong on November 11. Hide Caption 48 of 160 Photos: Hong Kong unrest People react after tear gas was fired by police during a protest in Hong Kong's Central District on November 11. Hide Caption 49 of 160 Photos: Hong Kong unrest Riot police face off with protesters at an entrance of a shopping mall during a demonstration on November 10. Hide Caption 50 of 160 Photos: Hong Kong unrest A man is helped by a volunteer medic after police used pepper spray during a demonstration on November 10. Hide Caption 51 of 160 Photos: Hong Kong unrest Students of the Hong Kong University of Science and Technology (HKUST) participate in a march on November 8, after hospital officials confirmed the death of student Chow Tsz-lok , 22. Police say Chow, a computer sciences student at HKUST, fell from the third floor to the second floor of a parking garage in the residential area of Tseung Kwan O in the early hours of November 4. Hide Caption 52 of 160 Photos: Hong Kong unrest A person places a flower at a memorial for 22-year-old Hong Kong university student Chow Tsz-lok on November 8. Hide Caption 53 of 160 Photos: Hong Kong unrest Students in gas masks are seen during a graduation ceremony at the Chinese University of Hong Kong on Thursday, November 7 in Hong Kong. Hide Caption 54 of 160 Photos: Hong Kong unrest Firefighters stand outside the offices of China's Xinhua News Agency after its windows were damaged by protesters in Hong Kong on Saturday, November 2. Hong Kong riot police fired multiple rounds of tear gas and used a water cannon Saturday to break up a rally by thousands of masked protesters demanding autonomy after Beijing indicated it could tighten its grip on the Chinese territory. Hide Caption 55 of 160 Photos: Hong Kong unrest Richard Chan, a candidate for the district council elections, reacts after being pepper-sprayed by police in Hong Kong on November 2. Hide Caption 56 of 160 Photos: Hong Kong unrest Thousands of black-clad masked protesters streamed into Hong Kong's central shopping district for another rally on November 2. Hide Caption 57 of 160 Photos: Hong Kong unrest A person dressed as President Donald Trump waves an American flag on a street in Hong Kong on Thursday, October 31, 2019. Hong Kong authorities braced as pro-democracy protesters urged people on Thursday to celebrate Halloween by wearing masks on a march in defiance of a government ban on face coverings Hide Caption 58 of 160 Photos: Hong Kong unrest A man dressed as the Joker for Halloween walks past police officers on October 31. Hide Caption 59 of 160 Photos: Hong Kong unrest Pro-democracy activist Joshua Wong (second from left) and Kelvin Lam (second from right) shout slogans as they meet the media outside the Legislative Council (LegCo) in Hong Kong on October 29, 2019, after Wong was barred from standing in an upcoming local election. Hide Caption 60 of 160 Photos: Hong Kong unrest A protester throws a tear gas canister on October 27 in Hong Kong. Hide Caption 61 of 160 Photos: Hong Kong unrest A couple wearing Guy Fawkes masks watch a rally at Chater Garden in Hong Kong on October 26. Hide Caption 62 of 160 Photos: Hong Kong unrest Protesters start a fire in front of the MTR station during demonstration on October 27. Hide Caption 63 of 160 Photos: Hong Kong unrest Tear gas smoke is seen exploding over reporters during an anti-government protest in Mong Kok district in Hong Kong on October 27. Hide Caption 64 of 160 Photos: Hong Kong unrest High school students take part in a human chain rally outside Kowloon park in Hong Kong on October 25. Hide Caption 65 of 160 Photos: Hong Kong unrest Police fire blue dye toward protesters in Hong Kong on Sunday, October 20. Blue dye can be used to stain and identify masked protesters. Hide Caption 66 of 160 Photos: Hong Kong unrest A pro-democracy protester is arrested by police on October 20. Hide Caption 67 of 160 Photos: Hong Kong unrest Pro-democracy lawmakers protest as Hong Kong Chief Executive Carrie Lam delivers a speech at the Legislative Council on Wednesday, October 16. Lam's annual policy address ended in chaos as pro-democracy lawmakers repeatedly disrupted her speech and heckled her with calls to honor the demands of anti-government protesters. Hide Caption 68 of 160 Photos: Hong Kong unrest A protester shoots a basketball at a poster of Lam during a rally on Tuesday, October 15. Hide Caption 69 of 160 Photos: Hong Kong unrest Protesters set fire to a Bank of China branch on Sunday, October 13. It was the 19th consecutive weekend of anti-government protests in Hong Kong. Hide Caption 70 of 160 Photos: Hong Kong unrest Protesters use the lights on their phones during a rally in central Hong Kong's business district. Hide Caption 71 of 160 Photos: Hong Kong unrest A protester attempts to break a tourist bus window on October 13. Hide Caption 72 of 160 Photos: Hong Kong unrest Protesters wearing masks in defiance of a recently imposed ban gather at a shopping mall on October 13. Hide Caption 73 of 160 Photos: Hong Kong unrest Supporters surround a police bus carrying political activist Edward Leung as it leaves the High Court in Hong Kong on Wednesday, October 9. Several hundred masked protesters gathered at Hong Kong's High Court for the appeal hearing of Leung, who was sentenced to six years in prison for his part in a violent clash with police. Hide Caption 74 of 160 Photos: Hong Kong unrest A woman is treated after police fired tear gas to disperse protesters in the Mong Kok district of Hong Kong on October 7. Hide Caption 75 of 160 Photos: Hong Kong unrest Pro-democracy protesters gather in a shopping mall on October 7. Hide Caption 76 of 160 Photos: Hong Kong unrest Rescue personnel check the bottom of a taxi after the driver allegedly drove onto the pavement, hitting protesters in Hong Kong on October 6. Hide Caption 77 of 160 Photos: Hong Kong unrest A China Construction Bank is seen vandalized in the Causeway Bay area of Hong Kong on October 6. Hide Caption 78 of 160 Photos: Hong Kong unrest Pro-democracy protesters set fires in the street in the Causeway Bay area. Hide Caption 79 of 160 Photos: Hong Kong unrest People protest the ban against masks on Saturday, October 5. Hide Caption 80 of 160 Photos: Hong Kong unrest An anti-government protester stands near a fire on Friday, October 4. Hide Caption 81 of 160 Photos: Hong Kong unrest Protesters move a statue depicting a protester armed with gas mask, helmet and umbrella on the streets of Hong Kong on October 4. Hide Caption 82 of 160 Photos: Hong Kong unrest Protesters set a fire at a China Construction Bank. Hide Caption 83 of 160 Photos: Hong Kong unrest Protesters spray paint slogans at the entrance to a tunnel on October 4. Hide Caption 84 of 160 Photos: Hong Kong unrest A store is in shambles after being vandalized by protesters. Hide Caption 85 of 160 Photos: Hong Kong unrest Pro-democracy demonstrators hold up their hands to symbolize their five demands during a rally on October 4. Hide Caption 86 of 160 Photos: Hong Kong unrest Protesters throw petrol bombs at the gate to the Tsuen Wan police station on Wednesday, October 2. Hide Caption 87 of 160 Photos: Hong Kong unrest Schoolmates of a student who was shot in the chest by police place their hands on their chests during a protest on October 2. Hide Caption 88 of 160 Photos: Hong Kong unrest A young protester was shot Tuesday, October 1, as violent protests erupted across Hong Kong on the 70th anniversary of the People's Republic of China. The incident marked a major escalation in violence that could galvanize the protest movement in Hong Kong. Hide Caption 89 of 160 Photos: Hong Kong unrest Police detain an anti-government protester on October 1. Thousands of black-clad protesters marched in central Hong Kong as part of multiple pro-democracy rallies. Hide Caption 90 of 160 Photos: Hong Kong unrest Police tackle and arrest pro-democracy protesters during clashes on October 1. Hide Caption 91 of 160 Photos: Hong Kong unrest A protester is seen carrying rocks on a street on October 1. While events in Beijing were being held to mark the 70th anniversary of the founding of the People's Republic of China, demonstrators rallied throughout Hong Kong. Hide Caption 92 of 160 Photos: Hong Kong unrest Protesters react after police fired tear gas near the central government offices in Hong Kong's Admiralty area on October 1. Hide Caption 93 of 160 Photos: Hong Kong unrest Pro-democracy protesters form a "Pepe the Frog" themed human chain on Monday, September 30. Hide Caption 94 of 160 Photos: Hong Kong unrest A man is detained by Hong Kong police during a protest in the Causeway Bay shopping district on Sunday, September 29. Hide Caption 95 of 160 Photos: Hong Kong unrest Bus passengers look at a burning barricade lit by pro-democracy protesters in front of the Mong Kok police station on Sunday, September 22. Hide Caption 96 of 160 Photos: Hong Kong unrest Pro-democracy protesters sing songs and chant slogans during a rally inside a shopping mall on September 22. Hide Caption 97 of 160 Photos: Hong Kong unrest A pro-China supporter, center, is escorted by police after confronting journalists in Hong Kong on September 15. Hide Caption 98 of 160 Photos: Hong Kong unrest Pro-government and anti-government supporters chant against one another at a shopping mall in Hong Kong on Friday, September 13. The sign translates to "Stop violence and curb chaos; safeguard Hong Kong." Hide Caption 99 of 160 Photos: Hong Kong unrest Demonstrators hold up their cell phone lights as they form a human chain at the Peak, a tourist spot in Hong Kong, on September 13. Hide Caption 100 of 160 Photos: Hong Kong unrest Police escort an injured man after he attacked protesters outside Prince Edward station in Hong Kong on Friday, September 6. Hide Caption 101 of 160 Photos: Hong Kong unrest Protesters burn paper money to pay their respects to injured protesters. Hide Caption 102 of 160 Photos: Hong Kong unrest Protesters prepare to clash with police outside the Mong Kok police station on September 6. Hide Caption 103 of 160 Photos: Hong Kong unrest A protester is detained by police at the Po Lam Mass Transit Railway station on Thursday, September 5. Hide Caption 104 of 160 Photos: Hong Kong unrest A man watches televisions at a store in Hong Kong as Chief Executive Carrie Lam announces the withdrawal of the extradition bill on Wednesday, September 4. Hide Caption 105 of 160 Photos: Hong Kong unrest A woman gets emotional on September 4 while paying her respects to protesters who were injured a few days earlier. Hide Caption 106 of 160 Photos: Hong Kong unrest Demonstrators travel through a railway station during a rally on Tuesday, September 3. Hide Caption 107 of 160 Photos: Hong Kong unrest Students wearing gas masks and helmets hold a banner that reads "five major demands are indispensable" at St. Francis' Canossian College in Hong Kong. Hide Caption 108 of 160 Photos: Hong Kong unrest Protesters gather in the bus terminal at Hong Kong International Airport on Sunday, September 1. Hundreds of pro-democracy activists attempted to block transport routes to the city's airport. Hide Caption 109 of 160 Photos: Hong Kong unrest A passenger walks to the airport on September 1 as pro-democracy protesters blocked a road outside the airport. Hide Caption 110 of 160 Photos: Hong Kong unrest A protester uses a slingshot outside the Central Government Complex during clashes with police on Saturday, August 31. Thousands of pro-democracy protesters held an anti-government rally one day after several leading activists and lawmakers were arrested in a sweeping crackdown. Hide Caption 111 of 160 Photos: Hong Kong unrest Protesters light a Molotov cocktail on August 31. Hide Caption 112 of 160 Photos: Hong Kong unrest Protesters take cover as policemen fire blue-colored water on them. Blue dye can be used to stain and identify masked protesters. Hide Caption 113 of 160 Photos: Hong Kong unrest A surveillance camera is covered with white paint during protests. Hide Caption 114 of 160 Photos: Hong Kong unrest An overhead view shows protesters reacting after police fired tear gas on August 31. Hide Caption 115 of 160 Photos: Hong Kong unrest Pro-democracy activists Agnes Chow and Joshua Wong speak to the media after they were released on bail at the Eastern Magistrates Courts on Friday, August 30. They were arrested earlier the same day in a dragnet across Hong Kong. Hide Caption 116 of 160 Photos: Hong Kong unrest Protesters clash with police after a rally in Hong Kong's Tsuen Wan district on Sunday, August 25. It was one of the most violent nights seen in Hong Kong since mass protests began in June. Hide Caption 117 of 160 Photos: Hong Kong unrest A police officer aims a gun in front of a protester on August 25. Hide Caption 118 of 160 Photos: Hong Kong unrest Some protesters shine laser pointers at police lines on August 25. Hide Caption 119 of 160 Photos: Hong Kong unrest Protesters pick up bricks to be used as projectiles on August 24.

Hide Caption 120 of 160 Photos: Hong Kong unrest Police retreat after clashing with protesters on August 24. Hide Caption 121 of 160 Photos: Hong Kong unrest Cell phones shine from the top of Lion Rock on August 23. Hide Caption 122 of 160 Photos: Hong Kong unrest Protesters march under umbrellas on Sunday, August 18. Hide Caption 123 of 160 Photos: Hong Kong unrest Tens of thousands of protesters showed up in the streets on August 18. Hide Caption 124 of 160 Photos: Hong Kong unrest A protester participates in a march on Saturday, August 17. His eye is covered with red gauze, referencing a woman who was allegedly shot in the eye with a beanbag round during clashes between protesters and police. Hide Caption 125 of 160 Photos: Hong Kong unrest Protesters point lasers at the Sham Shui Po police station on August 14. Hide Caption 126 of 160 Photos: Hong Kong unrest A police officer falls over an airport luggage trolley during a scuffle with pro-democracy protesters on Tuesday, August 13. For two days, protesters flooded the airport. Check-ins were suspended and dozens of outgoing flights were canceled. Hide Caption 127 of 160 Photos: Hong Kong unrest A traveler passes her luggage to security guards as she tries to enter the departures gate. Hide Caption 128 of 160 Photos: Hong Kong unrest A display board shows canceled flights on August 13. Hide Caption 129 of 160 Photos: Hong Kong unrest Medics look after a woman who received a facial injury during clashes on Sunday, August 11. Hide Caption 130 of 160 Photos: Hong Kong unrest A pro-democracy protester is held by police outside the Tsim Sha Tsui police station on August 11. Hide Caption 131 of 160 Photos: Hong Kong unrest Police fire tear gas at protesters during a demonstration in the Wong Tai Sin District on Monday, August 5. Hide Caption 132 of 160 Photos: Hong Kong unrest A train passenger gestures toward a protester, right, who was preventing the doors of a train from closing on August 5. The protester was trying to disrupt Hong Kong's morning rush-hour commute. Hide Caption 133 of 160 Photos: Hong Kong unrest A man comforts his pregnant wife near a train platform after protesters blocked the train doors on August 5. Hide Caption 134 of 160 Photos: Hong Kong unrest A protester stands in tear gas during a confrontation with police in the early hours of Sunday, August 4. Hide Caption 135 of 160 Photos: Hong Kong unrest A Chinese flag floats in water after it was thrown by protesters during a demonstration on Saturday, August 3. Hide Caption 136 of 160 Photos: Hong Kong unrest Members of Hong Kong's medical sector attend a protest in Edinburgh Place on Friday, August 2. Hide Caption 137 of 160 Photos: Hong Kong unrest The emblem on the China Liaison Office is protected by plexiglass during a demonstration on Sunday, July 28. Hide Caption 138 of 160 Photos: Hong Kong unrest A protester flees from baton-wielding police in the Yuen Long district of Hong Kong on Saturday, July 27. Hide Caption 139 of 160 Photos: Hong Kong unrest A protester looks through umbrellas during the clashes with police on July 27. Hide Caption 140 of 160 Photos: Hong Kong unrest Travelers watch as protesters rally at Hong Kong's international airport on Friday, July 26. Hide Caption 141 of 160 Photos: Hong Kong unrest Protesters clash with police on Sunday, July 21. Hide Caption 142 of 160 Photos: Hong Kong unrest Masked men in white T-shirts are seen after attacking anti-extradition bill demonstrators at a train station in Yuen Long. Hide Caption 143 of 160 Photos: Hong Kong unrest Medical workers help a protester affected by tear gas on July 21. Hide Caption 144 of 160 Photos: Hong Kong unrest The office of pro-Beijing lawmaker Junius Ho was trashed by protesters in Hong Kong's Tsuen Wan district. Hide Caption 145 of 160 Photos: Hong Kong unrest Police officers use pepper spray to disperse protesters after a rally in the Sheung Shui district on Saturday, July 13. Hide Caption 146 of 160 Photos: Hong Kong unrest A demonstrator sprays paint inside a chamber at Hong Kong's Legislative Council building, where protesters forced their way in on Monday, July 1. Hide Caption 147 of 160 Photos: Hong Kong unrest A protester smashes a window of the Legislative Council building. Hide Caption 148 of 160 Photos: Hong Kong unrest Columns of sunlight are cast on a crowd during the march on July 1. Hide Caption 149 of 160 Photos: Hong Kong unrest Helicopters carrying the flags of China and Hong Kong fly over demonstrators on July 1. Hide Caption 150 of 160 Photos: Hong Kong unrest A police officer uses pepper spray during a clash with protesters on July 1. Hide Caption 151 of 160 Photos: Hong Kong unrest A protester wearing a T-shirt with the word "revolution" walks past an inscription on a road that reads "Long Live HK." Hide Caption 152 of 160 Photos: Hong Kong unrest Police detain protesters near the government headquarters in Hong Kong on July 1. Hide Caption 153 of 160 Photos: Hong Kong unrest An overhead view shows thousands of protesters marching through a Hong Kong street on Sunday, June 16. Hide Caption 154 of 160 Photos: Hong Kong unrest Protesters run after police fired tear gas on Wednesday, June 12. Hide Caption 155 of 160 Photos: Hong Kong unrest By the morning of June 12, tens of thousands of mainly young people had arrived in the area, blocking streets and bringing central Hong Kong to a standstill. Hide Caption 156 of 160 Photos: Hong Kong unrest A demonstrator holds a sign during the June 12 rally. Hide Caption 157 of 160 Photos: Hong Kong unrest Police officers charge toward protesters during clashes on Monday, June 10. It was a continuation of protests that started the day before. Hide Caption 158 of 160 Photos: Hong Kong unrest Protesters on June 9 waved placards and wore white -- the designated color of the rally. "Hong Kong, never give up!" some chanted. Hide Caption 159 of 160 Photos: Hong Kong unrest Students wear chains during a demonstration on Saturday, June 8. Hide Caption 160 of 160

The legislation has not been used in more than half a century and gives Lam the power to bypass the city's legislature to "make any regulations whatsoever which he (or she) may consider desirable in the public interest." Lam said the new law was subsidiary legislation and so will be debated by the Legislative Council -- where pro-government parties hold a majority -- when they meet later this month.

Introduced in 1922, the law was last used in 1967 during the leftist riots, that were followed by a campaign of terrorist bombings across Hong Kong and pitched battles between protesters and police. Fifty-one died throughout the turmoil, including 10 police officers.

The new law bans people from wearing facial coverings that obscure their identity, including paint, at unauthorized or authorized protests, or public processions. Those found guilty face up to a year in prison and a HKD $25,000 ($3,100) fine.

Lam said the regulation contains exemptions for people who do have legitimate reasons to wear face coverings -- such as for religious, medical, or professional purposes.

Defiant protesters

What originally started out as a peaceful march descended into chaos on Friday evening -- with MRT stations burned, the Bank of China set on fire and police attacked in the streets.

Senior Superintendent Yolanda Yu confirmed a man had been shot and was undergoing surgery.

"At this point, the man is in surgery. We need to further investigate. We cannot investigate now because we cannot contact the man who was shot," she told reporters.

An earlier statement from Hong Kong police said an angry mob of protesters had thrown petrol bombs at a police officer, before trying to take his pistol which had dropped on the ground.

Protesters vandalized a number of areas in Hong Kong on Friday night.

Police said the incidents "poses a serious threat to public peace and order," and that officers will deploy "appropriate force to disperse the rioters."

Tear gas was deployed across Hong Kong to disperse the crowds, but fires continue to rage on throughout the territory.

In response to the escalation in violence, MTR spokesperson Brian Chow confirmed that all rail and subway transport services had been shut down.

Chow said there was no plan to re-open the stations at this stage, and that the MTR was "still analyzing" the number of stations that were set ablaze.

The closure affects 161 stations across Hong Kong.

All masked protesters risk being arrested from midnight on Friday, once the emergency law comes into effect. If arrested, they could face a year in prison.

Mounting pressure

Lam is facing mounting pressure to end the ongoing protests, which are set to enter their 18th weekend. Protests in the semi-autonomous city have grown increasingly violent since they began in early June.

Lam said that "rioters are attacking different parts of Hong Kong, wreaking terror" and that everyday life had been affected.

Hong Kong's Secretary of Security John Lee said at the press conference Friday that protesters acted more aggressively when they wore masks and it allowed those committing criminal acts to escape legal action.

"We can see that almost all violent protesters are masked to avoid police arrests and legal consequences, so they could assault people with different opinion, vandalize shops and MTR stations," Lee said.

But critics say the law would set a dangerous precedent and pave the way for harsher regulations.

Jason Ng, convenor of the Progressive Lawyers Group, said the "most troubling aspect of the mask ban is the slippery slope argument."

"This time it is a ban on masks, next time it can be a curfew or martial law," he said.

"The Emergency Regulations Ordinance grants extensive powers for the Chief Executive to pass measures on the vague grounds of 'public emergency' and 'serious public disorder.' These are not defined terms and can be interrupted broadly. Even more dangerously, there is no telling when these circumstances will cease to exist."

Ng added that the ban "will have a chilling effect on the more moderate participants from participating."

The Civil Human Rights Front, whose marches have attracted hundreds of thousands of people, said the anti-mask law would "further suppress citizens and aggravate the contradiction between society and the political power, further pushing Hong Kong into the abyss."

"Many citizens, including but not limited to grassroots workers, whistleblowers from different sectors and people of different sexual orientations, prefer to wear masks when they speak at public assemblies, in order to avoid discrimination against their identity and political consequence they would face," the group said in a statement.

Critics say the law would set a dangerous precedent.

However Chinese state media CCTV published a statement from the Hong Kong Macao Affairs office which said "under the current circumstance, it's legitimate and reasonable for the SAR government to adopt the anti-mask law, and it is crucial."

Spokesman Yang Guang added that "it won't undermine all the rights that Hong Kong people have enjoyed, including the freedom of assembly and demonstration."

Speaking to CNN last week , a senior adviser to Hong Kong leader Carrie Lam -- who spoke on background to be candid about government thinking -- said they were concerned that any declaration of an emergency by the Hong Kong government could enable Beijing to intervene . The laws which cover the central government doing so are all structured around an emergency situation.

"Declaring an emergency would bring on so much opposition from everywhere, bring you a step closer to Beijing intervention," the adviser told CNN. "If we ourselves declare there is a state of emergency we're halfway there."

Lam however, insisted Friday that Hong Kong was not under a state of emergency.

The announcement comes after an officer fired a live round into a protester for the first time Tuesday , when thousands took to the streets as Beijing celebrated the 70th anniversary of the founding of the People's Republic of China.

The day was marked by violent pitched battles that saw black-clad protesters hurled petrol bombs, set fire to subway station entrances and trash cans, and vandalized government and public buildings. Police responded using tear gas, rubber bullets, water cannons and arresting 269 people.

The teenage protester who was shot is under arrest for assaulting a police officer and could face further arrests for rioting, a source told CNN. He is in stable condition the Queen Elizabeth Hospital's media department said Wednesday.

The political crisis began after hundreds of thousands took to the streets to oppose a controversial bill that would have legalized extradition from Hong Kong to mainland China. The city's leader, Carrie Lam, has promised to withdraw the bill once the city's legislature resumes. But the movement has snowballed into a grassroots, decentralized crusade for universal suffrage and independent inquiries into alleged police misconduct.

In total since the anti-government protests began in June, 1,100 people have been injured, including 300 police officers, Lam said.