Hong Kong experienced “one of the most violent days” in its history on Tuesday, the city’s police chief has said, as protesters clashed with police on the 70th anniversary of the founding of communist China.

More than 100 demonstrators were taken to hospital and 180 arrested, authorities said, while an 18-year-old protester who was shot in the chest by police at point-blank range was in a stable condition after surgery.

Police chief Stephen Lo defended the actions of the officer who shot teenager Tsang Chi-kin, an incident which was caught on camera by a student union group and sparked fresh protests outside the school Tsang attended on Wednesday.

Mr Lo told a news conference he was left saddened by Tuesday’s bloody scenes, some of the worst in the months-long political crisis.

“Our national day is supposed to be a day to celebrate and be happy,” he said. Instead, it had been “one of the most violent, chaotic days in the history of Hong Kong”.

Hong Kong protesters out in force after months of turmoil: In pictures Show all 32 1 /32 Hong Kong protesters out in force after months of turmoil: In pictures Hong Kong protesters out in force after months of turmoil: In pictures A protester throws a stone into a building at Hong Kong Polytechnic University on 11 November Reuters Hong Kong protesters out in force after months of turmoil: In pictures Police patrol the streets of Hong Kong the day after an officer shot a protester during a protest on 11 November EPA Hong Kong protesters out in force after months of turmoil: In pictures Riot police stand guard during a protest against police brutality in Hong Kong on 27 October EPA Hong Kong protesters out in force after months of turmoil: In pictures Protesters carry traffic cones to build a barricade during anti-government protests in Causeway Bay, Hong Kong on 11 November Reuters Hong Kong protesters out in force after months of turmoil: In pictures Protesters use obstacles and bricks to block a road in Hong Kong on 11 November AP Hong Kong protesters out in force after months of turmoil: In pictures Graffiti on a window smashed by student protesters in Hong Kong Polytechnic University AP Hong Kong protesters out in force after months of turmoil: In pictures Protesters carry US and British flags during a demonstration in Hong Kong on 11 November Reuters Hong Kong protesters out in force after months of turmoil: In pictures A protester throws a bottle of water as he is shrouded in tear gas during a demonstration in the Tsim Sha Tsui district of Hong Kong on 27 October Reuters Hong Kong protesters out in force after months of turmoil: In pictures Journalists take pictures of police officers as they move to disperse protesters in Hong Kong on 27 October Reuters Hong Kong protesters out in force after months of turmoil: In pictures An man lies injured after being attacked by protesters who suspected him of being an undercover police officer on 27 October EPA Hong Kong protesters out in force after months of turmoil: In pictures A man runs among tear gas during a protest in Hong Kong on 27 October Reuters Hong Kong protesters out in force after months of turmoil: In pictures Protesters gather on a field in the Tsim Sha Tsui district of Hong Kong on 27 October Reuters Hong Kong protesters out in force after months of turmoil: In pictures Pro-democracy protesters turn away from a fire lit outside the Causeway Bay Mass Rapid Transit (MTR) station in Hong Kong on 4 October Getty Hong Kong protesters out in force after months of turmoil: In pictures People rest near rows of riot police officers during a protest in Mong Kok, Hong Kong on 27 October Reuters Hong Kong protesters out in force after months of turmoil: In pictures Pro-democracy protesters hold umbrellas as police fire tear gas at them ouside Tai Koo MTR station in Hong Kong on 3 October Getty Hong Kong protesters out in force after months of turmoil: In pictures Hong Kong police fire a water cannon from the central government office at protesters during a mass rally on the 70th anniversary of the founding of communist China on October 1 AFP/Getty Hong Kong protesters out in force after months of turmoil: In pictures Protesters burn a Chinese national flag during a mass rally on the 70th anniversary of the founding of communist China on 1 October AFP/Getty Hong Kong protesters out in force after months of turmoil: In pictures Protesters remove signs celebrating the 70th anniversary of the founding of communist China during a mass rally in Hong Kong on 1 October AFP/Getty Hong Kong protesters out in force after months of turmoil: In pictures Cardboard boxes set alight by protesters burn in the streets of Hong Kong during a mass rally on the 70th anniversary of the founding of communist China on 1 October EPA Hong Kong protesters out in force after months of turmoil: In pictures An anti-China banner has been placed in a barricade during a mass rally on the 70th anniversary of the founding of communist China on 1 October EPA Hong Kong protesters out in force after months of turmoil: In pictures A pro-democracy protester runs away after police fire a tear gas canister in Hong Kong's Wong Tai Sin district on October 4 Reuters Hong Kong protesters out in force after months of turmoil: In pictures Protesters run after police fire tear gas during a mass rally on the 70th anniversary of the founding of communist China on 4 October AFP/Getty Hong Kong protesters out in force after months of turmoil: In pictures Pro-democracy protester take cover after police fire a tear gas canister in Hong Kong's Wong Tai Sin district on 4 October Reuters Hong Kong protesters out in force after months of turmoil: In pictures The rally comes after months of protests on the streets of Hong Kong which began in oppposition to a proposed extradition bill EPA Hong Kong protesters out in force after months of turmoil: In pictures The extradition bill would have allowed the government to extradite people to China if they were facing certain criminal charges AFP/Getty Hong Kong protesters out in force after months of turmoil: In pictures Opposition to the bill stems from the fear that the Chinese government would abuse this power for political or commercial reasons EPA Hong Kong protesters out in force after months of turmoil: In pictures Protesters soon came to demand greater freedom and universal suffrage under the One Country, Two Systems principle AFP/Getty Hong Kong protesters out in force after months of turmoil: In pictures Protesters are wearing black to symbolise opposition to China as they take to the streets in a "day of grief" while the Chinese state celebrates the 70th anniversary of its communist founding AFP/Getty Hong Kong protesters out in force after months of turmoil: In pictures A protester charges forward holding umbrellas as a mass rally breaks out in violence in Hong Kong on 1 October AFP/Getty Hong Kong protesters out in force after months of turmoil: In pictures A protester pours water on a tear gas canister fired by police during a mass rally on the 70th anniversary of the founding of communist China on 1 October Reuters Hong Kong protesters out in force after months of turmoil: In pictures A protester carries a vandalised Chinese flag through Hong Kong during a mass rally on the 70th anniversary of the founding of communist China on 1 October EPA Hong Kong protesters out in force after months of turmoil: In pictures Protesters carry a banner that denounces the celebration of the 70th anniversary of the founding of communist China on 1 October EPA

The officer who shot Tsang had feared for his life and made a “split-second” decision to open fire with live rounds, Mr Lo told reporters. Video of the incident shows the teenager was striking at the officer with a pole when he was hit.

Mr Lo refused to answer questions as to why the officer did not use other non-lethal means. “It was the attacker who decided to come so close,” he said. “He had no choice, he could only use the weapon that he had available.”

He described protesters as “rioters” who were intent on “all these sorts of criminal damages” including arson and assaulting police officers, 25 of whom had been injured.

But outside the Tsuen Wan Public Ho Chuen Yiu Memorial College – the secondary school which Tsang attended – students chanted anti-police slogans, shouting “murderer” and demanding accountability.

Several hundred people, including students striking in solidarity with their wounded classmate, held up placards and sat cross-legged outside the school in the Tsuen Wan district of the city.

One held a hand-written message condemning “thug police”. Others held their arms across the chest below their left shoulders, symbolising the location of Tsang’s gunshot wound.

“The Hong Kong police have gone trigger-happy and nuts,” pro-democracy politician Claudia Mo said.

Having repeatedly viewed video of the shooting, Ms Mo said: “The sensible police response should have been using a police baton or pepper spray, etc, to fight back.

“It wasn’t exactly an extreme situation and the use of live bullets simply cannot be justified.”

The shooting was the first using live rounds since the unrest began in June, although officers have fired warning shots in the past and protesters have been struck with non-lethal means including bean bag rounds.

More protests are planned in response, and there were reports of other schools seeing classroom boycotts on Wednesday in solidarity.

Meanwhile, municipal workers cleaned up streets across the city that had been battlegrounds late into the night on Tuesday. Protesters had set fires and vandalised some public utilities, while police deployed teargas and water cannon at various locations.

The MTR Corp became a target for attacks after it made the decision to shut nearly 50 stations to make it harder for protesters to move around.

By early Wednesday, all metro stations were open although some lines were running slower than normal as MTR workers tried to repair damage to prepare the service for the nearly 6 million people who use it every day.

The scenes on Tuesday contrasted dramatically from the highly orchestrated displays in Beijing, where military and civilian parades were held to mark the fact that Mao Zedong had founded the People’s Republic on that date in 1949.

Carrie Lam and a delegation of Hong Kong officials attended the Beijing celebrations in what was described as a show of unity with the central government, and Ms Lam smiled as a float representing Hong Kong passed by.