* Protesters met with tear gas as they attempt to flee
* Protesters defiant, say they will never surrender
* High Court overturns face mask ban
Hong Kong police fired rubber bullets and tear gas on Monday to pin back frantic anti-government protesters fleeing a university where hundreds were holed up with petrol bombs and other homemade weapons amid fears of a bloody crackdown.
Dozens, choking on the tear gas, tried to escape again and again from the Polytechnic University 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.
Protesters jump inside the Hong Kong Polytechnic University (PolyU) as they failed to leave the area after they were tear gassed by police during clashes in Hong Kong
Protesters attempt to leave the campus of Hong Kong Polytechnic University (PolyU) during clashes with police in Hong Kong
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. Some were pulled back into campus by other protesters.
"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.
"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."
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.
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.
"Remember you have life in your hands. Why do you need to push us to death?" one person shouted at police from a campus rooftop as protesters wearing gas masks and clutching umbrellas looked for ways to escape.
Live video showed protesters with their hands tied behind their backs sitting cross-legged on a road as riot police stood guard in one of the busiest commercial and tourist districts in the former British colony.
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 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.
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 Defence Ministry spokesman Wu Qian said their efforts were welcomed by Hong Kong citizens.
The Hong Kong garrison "has the determination, confidence and capabilities to safeguard sovereignty, security and development interests of Hong Kong in accordance with the Basic Law and the Garrison Law and to ensure long term prosperity and stability in Hong Kong”, Wu said, speaking on the sidelines of a defence conference in Bangkok.
The Basic Law is the mini-constitution setting the terms for the formula under which the former colony returned to China.
The Hong Kong government involved a colonial-era emergency law in October banning faced masks commonly used by protesters. The High Court ruled on Monday the ban was "incompatible with the Basic Law".
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.
As police approached the barricaded front gate of the university before dawn, protesters retreated into the campus and started fires at the gate and a footbridge.
Some protesters discussed trying to leave, while others reinforced barricades and carried boxes of petrol bombs to positions around the complex.
Some of those trapped on the sprawling red-brick campus said they would never surrender.
"We need to fight until the end. If we don’t fight, Hong Kong will be over," said Ah Lung, 19.
The unrest in Hong Kong poses the gravest popular challenge to Chinese President Xi Jinping since he came to power in 2012. Xi has said he is confident Hong Kong's government can resolve the crisis.
Beijing denies interfering in Hong Kong's affairs and has blamed Western countries for stirring up unrest.
Investment bank Goldman Sachs announced that due to "ongoing disruption” in Hong Kong, it was postponing a party to mark the firm’s 150th anniversary. CEO David Solomon was due to attend.