Some anti-government protesters trapped inside a Hong Kong university have tried to flee through the sewers, where one student said she saw snakes, but fireman prevented the escape by blocking a trapdoor into the system.
Reuters witnesses said fewer than 100 protesters remained inside the Polytechnic University on Wednesday, ring-fenced 24 hours a day by riot police and barricades, after more than 1000 were arrested since late on Monday.
Some surrendered while others were grabbed in escape attempts that included trying to clamber down ropes to waiting motorbikes.
Some protesters, wearing waterproof boots and carrying torches, resurfaced inside the campus on Wednesday after unsuccessfully probing the sewers - where fast-rising water levels are also a hazard - for a way out during the night.
It was unclear if any had managed to escape that way.
Firefighters, who the students let onto the campus, were in place to stop any further such attempts to flee, blocking the only feasible entrance into the sewer system in an underground car park.
Police searched for any escapees during the night with spotlights, without resorting to the tear gas and rubber bullets, that marked clashes in recent days.
Hong Kong leader Carrie Lam has called for a humane end to a siege that saw the most intense clashes since the protests escalated more than five months ago.
They also tightened security in the streets around the university, making them safe enough for a late Tuesday visit by the force's new commissioner, Chris Tang, at the end of his first day on the job.
Police have made more than 5000 arrests in connection with the protests since June.
Chinese leaders say they are committed to the "one country, two systems" formula put in place in 1997 and have accused foreign countries, including Britain and the United States, of stirring up trouble.
British Foreign Secretary Dominic Raab condemned China's treatment of a former employee of Britain's Hong Kong consulate who told a newspaper Chinese secret police beat him seeking information about the protest movement.
Simon Cheng, a Hong Kong citizen who worked for the British mission's business-development team when he was detained, told the Wall Street Journal that he was questioned repeatedly about the role his interrogators presumed Britain was playing in fomenting the unrest.
"Simon Cheng was a valued member of our team. We were shocked and appalled by the mistreatment he suffered while in Chinese detention, which amounts to torture," Raab said, according to the Foreign and Commonwealth Office.
In Washington, the US Senate unanimously passed the "Hong Kong Human Rights and Democracy Act", which would require the secretary of state to certify at least once a year that Hong Kong retains enough autonomy to qualify for special US trading consideration and would impose sanctions against officials responsible for rights violations.
The bill must be reconciled with similar legislation approved by the House of Representatives. Senate aides said they expected it to move forward eventually as an amendment to a defence bill expected to pass Congress this year.
China's foreign ministry condemned the legislation, saying the United States should stop interfering in Hong Kong and Chinese affairs. The Hong Kong government expressed "deep regret" over it.
The unrest marks the most serious popular challenge to Chinese President Xi Jinping since he came to power in 2012.
Some protesters emerged as the sun rose above the campus to express a range of feelings, from defiance to uncertainty.
They still have stocks of petrol bombs, bows and arrows and other makeshift weapons after a weekend of fiery clashes.
The university on the Kowloon peninsula is the last of five that protesters had occupied to use as bases from which to disrupt the city over the past 10 days, blocking the central Cross-Harbour Tunnel outside and other arteries.