Several protesters have escaped from a Hong Kong university campus surrounded by police by abseiling from a bridge and fleeing on the back of motorbikes.
Around 100 others who tried to leave the Polytechnic University were met with tear gas and rubber bullets. Some were arrested.
Authorities say 116 people were injured in the violence on Monday.
In the past week, the campus has become the latest battleground for long-running anti-government protests.
The violence is some of the worst seen during months of unrest in the semi-autonomous Chinese territory. The protests started over a controversial extradition bill, and have now evolved into broader anti-government demonstrations.
China has warned that "no-one should underestimate [its] will to safeguard its sovereignty and Hong Kong's stability", and its ambassador to the UK said the central government would not sit back and watch if the situation became "uncontrollable".
Hong Kong is a part of China, and the protests are, in part, about the fear that the special freedoms the territory enjoys as a former British colony are being eroded.
On Monday, Hong Kong's High Court ruled that a ban on protesters wearing face masks was unconstitutional. The colonial-era emergency law was invoked in October, but protesters largely defied it.
Hong Kong's government said the weekend's events had "reduced the chance" of district elections being held on Sunday as planned, public broadcaster RTHK reports. Postponing or cancelling the vote could further inflame the protests.
The UK has urged an "end to the violence and for all sides to engage in meaningful political dialogue" ahead of the elections.
What is happening?
Police are still besieging the university where several hundred protesters are thought to be trapped. Officers have ordered those inside to drop their weapons and surrender.
A protester inside the university told the BBC supplies, including first aid equipment, were running low.
Meanwhile, a fire broke out on campus and loud explosions were heard, according to the South China Morning Post.
PolyU has been occupied by protesters for several days. On Sunday night, police warned protesters they had until 22:00 (14:00 GMT) to leave the campus, saying they could use live ammunition if the attacks continued.
On Sunday, the university said it had been "severely and extensively vandalised".
A number of protesters left inside the university have identified themselves as current students in media interviews but it is unclear exactly how many of them are, in fact, university students.
Tears and pride
By Grace Tsoi, BBC News, Hong Kong
Worried parents whose children were trapped inside the Polytechnic University were among the 200 protesters who joined a peaceful rally on Monday night in eastern Tsim Sha Tsui, a tourist area which is only 300 metres away from the besieged campus.
Ms Ng – who only wanted to be identified by her last name – found out on Sunday night her son was among those trapped inside. "He's frightened because he has not faced any emergency situation on his own. She has been on the streets near the university since then.
The teary-eyed mother is proud of her 18-year-old son despite the circumstances. "My son didn't cry. He's strong and likes to help others," she said. "I told my son that you did nothing wrong and you are an outstanding kid. I wouldn't blame you."
She told him to stay inside the campus and wait for her to pick him up. Ms Ng said the government should bear the responsibility for the chaos in Hong Kong.
"Our government is more and more reckless. It ignores the very lowly demands from the citizens!" she said. "I wasn't born in Read More – Source