Hong Kong police laid siege to a university on Monday, firing rubber bullets and tear gas to pin back anti-government protesters armed with petrol bombs and other homemade weapons from fleeing amid fears of a bloody crackdown.
Dozens, choking on the tear gas, tried to leave the Polytechnic University by breaking through police lines after a night of mayhem in the Chinese-ruled city in which roads were blocked and a bridge was set on fire and a police officer was shot by a bow and arrow.
Many protesters, dressed in regular clothes and without gas masks, made runs for it, dodging tear gas canisters and sponge grenades, only to be forced back inside.
Some were arrested, tackled to the ground, as others scrambled and tripped over barricades and fences as police pointed guns at them and threw punches.
"The police might not storm the campus but it seems like they are trying to catch people as they attempt to run," Democratic lawmaker Hui Chi-fung told Reuters.
"It's not optimistic now. They might all be arrested on campus. Lawmakers and school management are trying to liaise with the police but failed."
Police were putting up barricades of their own to keep the protesters in one place. Earlier, police urged the protesters to "drop their weapons" and leave.
Police did not explain their tactics on Monday.
"We've been trapped here for too long. We need all Hong Kongers to know we need help," said Dan, a 19-year-old protester on the campus, as he burst into tears.
"I don't know how much longer we can go on like this. We may need international help."
One 24-year-old protester, who gave his name as "Be Patient", said he nearly suffocated in the crush.
"We couldn't move at all. The police didn't stop ... they still used rubber bullet and sponge rounds to attack us. We're talking about a distance of one meter."
There were also running battles in the nearby commercial area of Nathan Road where activists stopped traffic and forced shopping malls and stores to shut.
Police said a car tried to hit an officer in the nearby Yau Ma Tei district on Sunday night, reversing and trying again. Police fired a shot and the driver fled.
Thirty-eight people were wounded overnight on Sunday, the city's Hospital Authority said. Reuters witnesses saw some protesters suffering from burns from chemicals in jets fired from police water cannons.
Police said they fired three live rounds when "rioters" attacked two officers who were attempting to arrest a woman. No one was wounded and the woman escaped amid a dramatic escalation of the unrest that has plunged the Asian financial hub into chaos for almost six months.
Demonstrators are angry at what they see as Chinese meddling in Hong Kong's promised freedoms when it returned to Chinese rule in 1997. They say they are responding to excessive use of force by police.
China says it is committed to the "one country, two systems" formula granting Hong Kong autonomy, while the city's police deny accusations they use excessive force.
China's foreign ministry said on Monday no one should underestimate its will to protect its sovereignty and Hong Kong's stability.
The United States condemned the "unjustified use of force" in Hong Kong and called on Beijing to protect Hong Kong's freedom, a senior official in President Donald Trump's administration said.
Chinese soldiers in a base close to the university were seen on Sunday monitoring developments at the university with binoculars, some dressed in riot gear.
Chinese troops in shorts and T-shirts, some carrying red plastic buckets or brooms, emerged from their barracks on Saturday in a rare public appearance to help clean up debris.
Chinese troops have appeared on Hong Kong's streets only once since 1997, to help clear up after a typhoon last year.
Asked about the clean-up operation, Chinese Defense Ministry spokesman Wu Qian said their efforts were welcomed by Hong Kong citizens.
The Hong Kong government invoked a colonial-era emergency law in October banning faced masks commonly used by protesters. The High Court ruled on Monday the ban was unconstitutional.
The city's Cross-Harbour Tunnel, next to the Polytechnic university, linking Hong Kong island to the Kowloon peninsula, remained closed after protesters torched a bridge above the toll booths on Sunday.
Some train services and many roads across the Kowloon peninsula were closed. All schools were shut.
The unrest poses the gravest popular challenge to Chinese President Xi Jinping since he came to power in 2012.
Beijing denies interfering in Hong Kong's affairs and has blamed Western countries for stirring up unrest.