Hong Kong leader Carrie Lam said 100 students were still trapped at a university in the city on Tuesday, as the violent standoff with police entered a third day.

Ms Lam urged the remaining demonstrators to lay down their makeshift weapons and give themselves up for arrest peacefully, suggesting it was the only route out of the situation.

Around 600 protesters left the Hong Kong Polytechnic University campus on Monday, she said, and 400 were arrested. The other 200 were under the age of 18 and, though not immediately arrested, could face charges in the future.

The university clashes have been some of the most brutal in Hong Kong’s months-long crisis. Protesters occupied it and other campuses last week before police advanced in large numbers on Sunday, triggering a three-day siege that raised fears of the prospect live ammunition would be used.

Footage from the scene showed protesters attempting to flee in large numbers to avoid arrest, with some using rope ladders to abseil down from a footbridge to waiting motorbikes below. It was unclear if any made it out without getting caught.

Speaking to reporters after a weekly meeting with advisers on Tuesday, Ms Lam said: “We will use whatever means to continue to persuade and arrange for these remaining protesters to leave the campus as soon as possible so that this whole operation could end in a peaceful manner.”

Ms Lam was also asked about the appearance of Chinese soldiers on the streets of Hong Kong over the weekend, when hundreds of troops left their barracks in the city to help clean up debris left by protesters.

Analysts called it a show of force from Beijing, while pro-democracy groups called the intervention – which was not formally requested by the Hong Kong government – a breach of the city’s laws.

Asked whether she would seek help from Chinese troops based in Hong Kong, Ms Lam insisted her government remains confident it is able to cope with the situation.

China expressed frustration on Tuesday at a decision by the Hong Kong high court to strike down Ms Lam’s ban on face masks for protesters, which was pushed through using colonial-era emergency regulations.

Hong Kong protests: Latest after court strikes down face mask ban Show all 24 1 /24 Hong Kong protests: Latest after court strikes down face mask ban Hong Kong protests: Latest after court strikes down face mask ban Police in riot gear move through a cloud of smoke as they detain a protester at the Hong Kong Polytechnic University AP Hong Kong protests: Latest after court strikes down face mask ban A protester takes cover under an umbrella Reuters Hong Kong protests: Latest after court strikes down face mask ban A protestor reacts to police officers EPA Hong Kong protests: Latest after court strikes down face mask ban Pro-democracy protesters react after the police fired tear gas outside the Hong Kong Polytechnic University EPA Hong Kong protests: Latest after court strikes down face mask ban A pro-democracy protester holds a placard EPA Hong Kong protests: Latest after court strikes down face mask ban Protesters react as police fire tear gas AFP via Getty Hong Kong protests: Latest after court strikes down face mask ban An anti-government protester is silhouetted during protests Reuters Hong Kong protests: Latest after court strikes down face mask ban Tear gas engulf umbrellas Reuters Hong Kong protests: Latest after court strikes down face mask ban A protester lowers himself down a rope from a bridge to a highway, to escape AFP via Getty Hong Kong protests: Latest after court strikes down face mask ban People form a human chain to pass materials as they gather for a march towards Hong Kong Polytechnic University AFP via Getty Hong Kong protests: Latest after court strikes down face mask ban Protesters are seen after leaving the campus of the Hong Kong Polytechnic University Reuters Hong Kong protests: Latest after court strikes down face mask ban Pro-democracy protesters during clashes with police outside the Hong Kong Polytechnic University EPA Hong Kong protests: Latest after court strikes down face mask ban Police spray blue-dyed liquid AP Hong Kong protests: Latest after court strikes down face mask ban Protesters are sprayed with blue liquid from water cannon during clashes with police outside Hong Kong Polytechnic University (PolyU) in Hong Kong, China, November 17, 2019. REUTERS/Tyrone Siu TYRONE SIU Reuters Hong Kong protests: Latest after court strikes down face mask ban Police officers detain a protester AP Hong Kong protests: Latest after court strikes down face mask ban An injured protester is evacuated by ambulance EPA Hong Kong protests: Latest after court strikes down face mask ban Injured people are taken away after clashes Getty Hong Kong protests: Latest after court strikes down face mask ban A protester throws back a tear gas canister fired by police at the Hong Kong Polytechnic University in Hong Kong on November 17, 2019. - Hong Kong police fired tear gas on November 17 morning at protesters intent on keeping their stranglehold on a major tunnel as pro-democracy activists vowed to "squeeze the economy" into next week. (Photo by Ye Aung Thu / AFP) (Photo by YE AUNG THU/AFP via Getty Images) YE AUNG THU AFP via Getty Hong Kong protests: Latest after court strikes down face mask ban Police arrest anti-government protesters Getty Hong Kong protests: Latest after court strikes down face mask ban A protester's umbrella is seen on fire during clashes with police outside Hong Kong Polytechnic University (PolyU) in Hong Kong, China November 17, 2019. REUTERS/Athit Perawongmetha ATHIT PERAWONGMETHA Reuters Hong Kong protests: Latest after court strikes down face mask ban Medical staff carry a protester out of the campus of Hong Kong Polytechnic University Reuters Hong Kong protests: Latest after court strikes down face mask ban Protesters try to extinguish a tear gas canister Reuters Hong Kong protests: Latest after court strikes down face mask ban Protesters take a rope down from a bridge to a highway, to escape from Hong Kong Polytechnic University campus AFP via Getty Hong Kong protests: Latest after court strikes down face mask ban A protestor gestures during a confrontation with police AP

The court had ruled that the ban went too far in restricting citizens’ rights, and was therefore unconstitutional.

Only China’s parliament had the authority to rule on constitutional matters in Hong Kong, claimed parliamentary spokesperson Zang Tiewei. “No other institution has the right to make judgments or decisions,” he said.