Hong Kong police have laid siege to a university, firing rubber bullets and tear gas to pin back anti-government protesters armed with petrol bombs and other weapons amid fears of a bloody crackdown.
Dozens, choking on the tear gas, tried to leave the Polytechnic campus by breaking through police lines.
Monday's stalemate of sorts followed a night of mayhem in the Chinese-ruled city in which roads were blocked, a bridge set on fire and a police officer was shot with an arrow.
Many protesters made runs for it, dodging tear gas canisters and sponge grenades only to be forced back.
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 MP Hui Chi-fung said.
"It's not optimistic now."
Police said officers had been deployed "on the periphery" of the campus for a week, appealing to "rioters" to leave.
"All our warnings were ignored," they said in a statement. "Our message was loud and clear, the violence has escalated to rioting."
They said "toxic and dangerous chemicals" had been stolen from the university laboratory.
"We must warn that the university campus has become a powder keg where danger is far beyond what we can estimate."
Police arrested 154 people aged between 13 and 54 over the weekend.
Dan, a 19-year-old on the campus, burst into tears as he said the protesters had been trapped for too long.
"We need all Hong Kongers to know we need help," he said. "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.
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 nearby Yau Ma Tei, reversing and trying again. Police fired a shot and the driver fled.
Thirty-eight people were wounded overnight on Sunday, the Hospital Authority said. Some suffered burns from chemicals in jets fired from police water cannons.
Police said they fired three live rounds when "rioters" attacked two officers attempting to arrest a woman.
No one was wounded and she escaped.
Demonstrators are angry at what they see as Chinese meddling in Hong Kong's promised freedoms when the then British colony returned to Chinese rule in 1997.
They say they are responding to excessive police force.
China says it is committed to the "one country, two systems" formula granting Hong Kong autonomy, while the city's police deny accusations of brutality and say they show utmost restraint.
Australian Associated Press