Yanny Man, 23, had no time to think about it before crawling over the ledge of a bridge, eight metres high, grabbing a rope and pushing off toward the ground below.

Behind her people shouted: “Just go, just go!” Police trying to stop them had paused from shooting teargas and were very likely to fire again.

She fell, hitting a road covered in broken glass, and lay paralysed with pain before someone scooped her up, put her on a motorbike and rushed her away.

“There were 50 people behind me, waiting for that one rope. We couldn’t hesitate,” she said. “This was my only chance to leave.”

Protesters leaving with medical staff from Hong Kong Polytechnic University (PolyU) on the fourth day of a standoff with police. Photograph: Jeon Heon-Kyun/EPA

Man was one of dozens of Hong Kong protesters who on Monday night made it out of a days-long police siege of Polytechnic University by abseiling off of a bridge to where cars and motorbikes awaited.

The red-brick campus in Kowloon has been taken over since last week by demonstrators rallying against their government and the police. On Sunday, police put it on lockdown and it has become the focus of one of the tensest and most violent confrontations since the protests began almost six months ago.

Hundreds of protesters have attempted to escape by making a run for it in groups, only to be beaten back by teargas, rubber bullets and water cannon. Dozens have been caught. As a result, the activists have sought more desperate measures, including crawling through sewage drains, jumping from a bridge and tunnelling under barriers.

Q&A Why have universities become a flashpoint in the Hong Kong protests? Show Hong Kong’s protest movement has evolved throughout the five months it has raged in the harbour city. Its latest phase is being played out on Hong Kong’s university campuses — traditionally sites of political activism — some of which have been transformed into makeshift fortresses by demonstrators in the past fortnight. The immediate trigger for the campus confrontations appears to have been the death on 8 November of a Hong Kong University of Science and Technology student. Since then, several campuses have been barricaded by students, some of who are using footbridges or or near the campuses to block roads. At least three campuses are blockaded, including the Hong Kong Polytechnic University, close to the cross-harbour tunnel — a key artery for traffic in the city, and one that authorities will be determined to keep open.

The campus protests have been desperate: activists are using petrol bombs, bamboo poles and other weapons including javelins and bows and arrows. Observers have told the Guardian the shift to campuses represents a major escalation. Many of those occupying the campuses are students or alumni, and until recently, riot police have refrained from entering universities. “The university is the home turf of the students,” Ho-Fung Hung, a professor in political economy at Johns Hopkins University, has told the Guardian. “There is this notion of academic freedom and the university as a bastion of free ideas, this notion of autonomy. To people, this should not be breached by authorities.”

Their desperate measures underline the protesters’ deep suspicion of Hong Kong police, whom they accuse of brutality, including sexual assault. The police have urged protesters to give themselves up and assured the public they are seeking a peaceful resolution. If arrested, protesters face rioting, among other charges, which could mean 10 years in prison.

On Wednesday, between a few dozen and a hundred Hong Kong protesters remained inside the university, many of them too scared to attempt escape or determined to stay until the end. As conditions within the campus deteriorate, those who have fled are urging their fellow demonstrators to also leave.

“We are trying our best to get them all out even though it’s getting harder,” said Wong, 21, a fourth year student at PolyU, as the university is known.

Wong also fled on Monday, when the police were distracted elsewhere on campus, leaving through an unguarded exit, crawling through brush and sprinting along an open road toward “parents’ cars”, volunteer drivers waiting nearby to rescue them.

Wong and Man send their friends still inside possible escape routes shared by current and former students who know the campus well. Wong says she tries to keep in constant communication with her friends at PolyU, but some have stopped communicating. “They are feeling a lot of pressure,” she said.

A diver enters a sewer to search for anti-government protesters trying to escape from the besieged Hong Kong Polytechnic University. Photograph: Anthony Wallace/AFP via Getty Images

Protesters inside say university staff have been checking buildings for people, while teachers have been brought in to persuade them to leave. On Wednesday, two crawled through a drainage tunnel but were stopped and arrested by police.

Food, water, and other supplies were already running low on Monday, when dozens made it out, as panic spread. In a desperate attempt to distract police, protesters burned barricades at the school’s entrance, abandoning a key defence.

“The situation inside the campus is worsening day by day. There are few first aiders and fewer supplies and the hygiene is quite bad,” said Kelvin, 21, a student at the university who also escaped on Monday. “I can’t imagine how my friends can manage to survive in that place for one or two days more.”

Protesters look for an exit at the campus of the Hong Kong Polytechnic University. Photograph: Thomas Peter/Reuters

Police have detained about 1,000 protesters from the university, including 300 minors, who were not arrested but could be investigated and charged later. After a day-long battle on Sunday during which protesters threw molotov cocktails and fired arrows , police labelled everyone inside as participating in a “riot”.

“Some of my friends inside are the most peaceful protesters – the people who pick up trash. They don’t know anything about fighting. They are stuck in there,” said Kelvin.

Protesters see the police’s approach to the university as a sign of a shift in strategy, focusing on students who drive the movement. But observers say it is a strategy likely to backfire.

Outside the university, thousands took to the streets on Monday trying to break the police perimeter to reach the protesters. Video footage showed police stomping on a demonstrator’s head and driving a van at demonstrators.

“So many people of all different kinds turned out, not just frontline protesters. It was a huge event,” said Kong Tsung-gan, a Hong Kong-based writer and activist. “The government and police can continue pounding us as hard as they want, but all it does is make them look bad and further alienate them from Hong Kong people.”

For the protesters who took over the university in order to block a nearby tunnel connecting Kowloon and Hong Kong and pledged to hold on to it as a bargaining chip, the result could be seen as a failure.

The experience of feeling trapped, as well as mass arrests and injuries – almost 300 people from the campus were taken to hospital – have depressed many, some of whom disagreed with the decision to occupy the university in the first place.

Still, they are reluctant to call it a setback. “We could be feeling down or lost for a short period of time, but I believe Hong Kong people will not surrender. We will not give up because a lot of people are sacrificing and a lot of people are doing so much for us,” said Man.

“I need a rest but I think after this I will be stronger,” she said.

Janice Hui contributed additional reporting