Hong Kong’s embattled leader, Carrie Lam, has warned that mass protests have pushed the region to the brink of a “very dangerous situation” as residents went on strike, paralysing the city.

Lam, who had disappeared from public view for two weeks, gave a media briefing in which she condemned the protests for damaging Hong Kong’s economy and stability.

Hong Kong protest: car rams protesters in Yuen Long – live updates Read more

“Such extensive disruptions in the name of certain demands or uncooperative movement have seriously undermined Hong Kong law and order and are pushing our city, the city we all love, and many of us helped to build, to the verge of a very dangerous situation,” she said.

On Monday, transport across Hong Kong was brought to a standstill and more than 150 flights out of the city were cancelled. Almost 100 outbound and 100 inbound flights were cancelled. Protesters also blocked key roads and stopped trains throughout the city.

As the city enters its ninth consecutive week of mass protests, tensions have escalated. Protesters clashed with police who fired tear gas to disperse them. Others reportedly fought with local residents.

In Yuen Long, the site of a violent attack on commuters on 21 July, a car rammed through a barricade set up by protesters, narrowly missing people trying to hold back the barrier, and injuring one person.

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Witnesses said a driver was stopped at a roadblock set by protesters near the Yoho Mall in Yuen Long. After an argument with protesters, the driver got back in his car and protesters tried to push against the vehicle to prevent him from leaving.

“The driver ignored them and continued to accelerate,” said Derek Man, who was on the road at the time, with the protesters. “The tyres emitted a lot of white smoke. The vehicle broke through the barrier and knocked down one person and then he left the scene.”

Play Video 0:44 One person injured after car rams protesters' barricade in Yuen Long, Hong Kong – video

Protesters have shifted tactics beyond only marches and protests in the streets. Civil servants from more than 30 government departments, as well as pilots, teachers, construction workers, engineers, and aviation staff all pledged to strike on Monday.

On Monday morning, several lines of the MTR, the rail network serving Hong Kong, were suspended as protesters, many wearing face masks and black clothing, blocked the doors of trains, preventing them departing the stations. There were also reports of discarded umbrellas being wedged in train doors to prevent them from closing, delaying services.

Seven districts were holding simultaneous rallies, with demonstrators filling up parks, shopping malls, and spilling over into nearby roads and bridges.

Thousands dressed in black, the signature colour of the protests, gathered at Tamar Park in Admiralty near government offices.

“I want Carrie Lam to come out and fix the problem, not give us some bullshit,” said Joel Tse, a 25-year-old advertising industry professional who said he had been on the fence as to whether or not he should join today’s general strike. After watching the chief executive’s press conference earlier today he decided to join.

At a shopping mall in Shatin, a district where previous clashes with police last month angered local residents, hundreds of protesters took over the high-end commercial centre forcing stores to shut. Crowds of protesters clad in black sat on the floor of the mall chanting: protesters shouted: “Hong Kong people, let’s go!”

Elsewhere in the city, protesters set up roadblocks and paralysed parts of the public transportation network.

While many of the rallies were peaceful, by late afternoon police had begun to clash with protesters. Police fired several rounds of tear gas and pepper spray at protesters who had gathered outside of a police station in the Tin Shui Wai in Hong Kong’s New Territories. Some were beaten with batons, according to footage, and at least four were arrested.

Monday’s planned city-wide protest, which is aimed to disrupt peak-hour travel of commuters, is the fifth consecutive day of mass demonstrations in the city. Simultaneous rallies were planned for seven of Hong Kong’s 18 districts on Monday. Hong Kong has not held a general strike in more than 50 years.

Faith Tang, 30, a teacher at a language school, said the principal had closed the centre that day because so many teachers and administrative staff had stayed home. Tang said she joined the strike in order to force the government to respond to the protesters’ demands, which includes a complete withdrawal of a controversial extradition bill.

She added that she joined the strike, “to stand with my fellow Hongkongers, to show support for our relentless fight for freedom and justice.”

Commuters going to work said they were supportive of the strike, even if they themselves could not participate.

“This is a last resort,” said Cindy Chan, waiting in a long bus line after her local train line suffered severe delays. Chan works in utilities and said she was unable to take time off from work. “The government doesn’t listen to the opinions of the people and later you can see it’s getting worse and worse,” she said.

The city-wide protests began over an extradition bill to send suspects to China, but have turned into a broader political movement for the semi-autonomous city, with residents demanding the protection of freedoms for Hongkongers and accountability from the Hong Kong government.

Flanked by members of her government, Lam said she had already responded to the protesters’ demands. “Some people may not agree with our response … but we have considered every factor. What is in front of us is Hong Kong’s stability and future and escalated violence,” she said.

Protesters say police are deploying harsher tactics against them and trying to arrest more demonstrators. On Sunday night and the early hours of Monday, police clashed with protesters and residents in various locations, after protesters evaded and frustrated the police by holding flashmob demonstrations throughout the city. Police have arrested more than 60 people and charged 44 of them with rioting, a crime that could mean up to 10 years in prison.

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On Monday, protesters braced for clashes with police as they continued to stage disruptions across the city.

“When Hong Kong people are going to the march, we know there’s a risk,” said one protester, Lam, who joined the strike on Monday. “Our tactic is ‘be water,’ and we don’t really know what exactly we are going to do next, as things change rapidly every day. We just do whatever we can and see how things go.”

Facebook Twitter Pinterest Protesters prevent the doors of a MTR underground train from closing at Fortress Hill station in Hong Kong. Photograph: Anthony Wallace/AFP/Getty Images

The former British colony, which reverted to Chinese control in 1997, is meant to enjoy a “high degree” of autonomy from the mainland as part of the “one country, two systems” framework, but residents say their freedoms are slowly disappearing under China’s influence.

On Sunday, people blocked Hong Kong’s cross-harbour tunnel and another group of protesters surrounded a police station in the outer district of Kwun Tong, where they shined lasers at the police and threw bricks at the compound. Earlier in the day, after a peaceful rally in Tseung Kwan O in Hong Kong’s New Territories, protesters broke the windows of a police station, using a makeshift catapult to launch objects at the building.

Karen Zhang (@karenised) At Lai King station, dozens of young people in black and masks have been blocking the trains to central and HK since 7:30am. Some passengers blamed them for stopping them for work. A middle aged man in blue pushed a protestor off the train which caused chaos #antiELAB pic.twitter.com/h7QmTRyySv

As fears rise that Beijing may intervene and quash the unrest, Hong Kongers have been watching Chinese state media carefully. On Sunday, Xinhua, a state-run news agency, published several articles condemning protesters, including one saying: “The central government will not sit idly by and let this situation continue.”