HONG KONG (Reuters) - Some anti-government protesters trapped inside a Hong Kong university on Wednesday tried to flee through the sewers, where one student said she saw snakes, but fireman prevented further escape bids by blocking a metal manhole into the system.

Reuters witnesses said fewer than 100 protesters remained inside the Polytechnic University, ring-fenced 24 hours a day by riot police and barricades, after more than 1,000 were arrested from 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 after unsuccessfully probing the sewers - where fast-rising water levels are also a hazard - for a way out during the night.

Police said six people were arrested on Wednesday - four people removing a manhole cover outside the campus and two climbing out.

Firefighters, whom the students let on to 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 on the campus.

“The sewer was very smelly, with many cockroaches, many snakes. Every step was very, very painful,” said Bowie, 21, a student at Hong Kong University who was forced to turn back.

“I’d never thought that one day I would need to hide in a sewer or escape through sewers to survive ... The most unforgettable feeling is the fear when I was inside.”

She said she and friends were in the dirty water for about an hour, only to find they were no closer to escape.

“When we reached the end, we found we were still in the poly,” she said.

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.

‘FAIR AND HUMANE’

Police said nearly 800 people had left the campus peacefully by late on Tuesday and they would be investigated, including nearly 300 under the age of 18.

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.

Police said they had no plans to storm the campus.

“We are hopeful that this incident will come to a peaceful end in the near future,” university president Teng Jin-guang told reporters.

Police 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.

Tang is under pressure to restore police morale as well as public confidence in a force that has come in for widespread criticism for increasingly violent tactics. Police deny accusations of using excessive force.

Police have made more than 5,000 arrests in connection with the protests since June.

The number of criminal damage cases reported between June and September was up 29.6% on the same period last year, Commerce Secretary Edward Yau said in a written statement. Arson cases were up 57.4%.

Tang earlier urged the support of all citizens to end the unrest triggered by fears that Beijing is stifling the former British colony’s freedoms and extensive autonomy guaranteed in its handover to Chinese rule in 1997.

Chinese leaders say they are committed to Hong Kong’s “one country, two systems” formula for autonomy and have accused foreign countries, including Britain and the United States, of stirring up trouble.

Ties between China and those two countries came under strain over Hong Kong on Wednesday.

British Foreign Secretary Dominic Raab condemned China’s treatment of Simon Cheng, a former employee of Britain’s Hong Kong consulate, who said secret police beat him seeking information about the protest movement.

‘TORTURE’ IN CHINA

“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.

A Chinese foreign ministry spokesman said Cheng had been detained for 15 days and had admitted fully to his offences. All of his legal rights were safeguarded, the spokesman said.

The U.S. 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 U.S. 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.

China summoned a representative of the U.S. embassy in Beijing over the legislation and demanded that the United States stop meddling, the foreign ministry said.

The Hong Kong government expressed “deep regret” over the bill.

The unrest marks the most serious popular challenge to Chinese President Xi Jinping since he came to power in 2012.

Protesters on the campus still have vast 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.

The Hong Kong Open golf tournament, scheduled for Nov. 28 to Dec. 1, has been postponed, the Asian Tour and European Tour said.

Hong Kong-based employees at two units of Chinese brokerage Haitong Securities – Haitong Capital Investment and Haitong International - joined a clean-up of roads in a Kowloon district, two people with knowledge of the matter said.

Haitong Capital said employees who helped with the clean-up could go home afterwards. The company offered rubber gloves, one said.