Several protesters have been arrested while trying to run from a Hong Kong university campus surrounded by police.
A group of around 100 people tried to leave Polytechnic University, but were met with tear gas and rubber bullets.
It is the third time protesters have tried to leave, following a fiery overnight stand-off with police.
In the past week, the campus has turned into a battleground as long-running anti-government protests become more violent.
Meanwhile, 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 the ban.
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.
At a news conference in Beijing, Chinese foreign ministry spokesman Geng Shuang said: “No-one should underestimate China’s will to safeguard its sovereignty and Hong Kong’s stability.”
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.
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’s Foreign Office has expressed concern, saying: “We need to see an end to the violence, and for all sides to engage in meaningful political dialogue ahead of the district council elections.”
What is happening?
The police are continuing to lay siege to the Polytechnic University where several hundred protesters are thought to be trapped. Officers have ordered those inside to drop their weapons and surrender.
Earlier, dozens tried to break out of the campus and through police lines. Some escaped while others were arrested.
A protester inside the university told the BBC that the situation was calm, but there was an underlying tension. He said supplies, including first aid equipment, were running low.
PolyU has been occupied by protesters for several days. On Sunday night, police warned protesters they had until 22:00 local time 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 in 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.
How did we get here?
Campuses remained relatively free of violence during the Hong Kong protests but, last week, the Chinese University of Hong Kong became a battleground.
Police said protesters threw petrol bombs on a major road near the university in an effort to stop traffic. Officers attempted to reclaim the road, leading to major clashes.
The university then cancelled all classes for the rest of the term. Days later, protesters at PolyU also tried to block access to a key tunnel near the university.
On Monday afternoon, the city’s Hospital Authority said 24 people aged between 16-84 were injured, with four in serious condition across Hong Kong.
Some 13 people, aged between 22 and 57, were injured on Sunday, with one in serious condition. It is unclear how many of the injured were protesters at the university.
Protests have also been held at other locations in Hong Kong.
Why are there protests in Hong Kong?
Hong Kong – a British colony until 1997 – is part of China under a model known as “one country, two systems”. Under this model, it has a high degree of autonomy and people have freedoms unseen in mainland China.
The protests started in June after the government planned to pass a bill that would allow suspects to be extradited to mainland China. Many feared this would undermine the city’s freedoms and judicial independence.
The bill was eventually withdrawn, but the demonstrations continued, having evolved into a broader protest movement against alleged police brutality, and the way Hong Kong is administered by Beijing.