Hong Kong CNN  — 

A small number of protesters remain inside a Hong Kong university campus that has been the site of a prolonged battle with police.

Hong Kong Polytechnic University (PolyU), on the southern tip of the Kowloon peninsula, has seen some some of the most violent and dramatic scenes in almost six months of anti-government demonstrations. Multiple arrests were made around the campus Monday, as protesters attempted to leave, only to be met with tear gas and rubber bullets.

As of Tuesday morning, about 300 protesters remained on campus, estimated Polytechnic University student union president Derek Liu.

The Red Cross said that it had evacuated at least six injured people from the campus overnight. The organization said some of the injured protesters had been suffering from suspected limb fractures, burn injuries and skin necrosis.

The threat of more violence continues to loom over the operation. On Monday afternoon, riot police were seen carrying what appeared to be assault rifles at a clearance operation in the nearby Jordan area of Kowloon. Police confirmed to CNN that the weapons were “ready to use.” The comments follow a statement Sunday in which police said they were prepared to fire live rounds if necessary.

Protesters have been holed up at the sprawling PolyU campus since last week, after an escalation in the months-long unrest that saw multiple universities across the city fortified and turned into temporary protest camps. They had used the PolyU campus as a base from which they launched operations to block nearby roads and the Cross Harbor Tunnel which connects Kowloon to Hong Kong Island.

The tunnel is the busiest of the city’s three harbor road crossings. According to 2017 government statistics, more than 110,000 vehicles use the Cross Harbor Tunnel every day.

An earlier attempt by police to clear the area on Sunday was met with fierce resistance, as protesters on the campus set huge fires to block the force’s advances and launched a barrage of petrol bombs, bricks and other missiles. One police officer was shot in the leg with an arrow, as the force responded with round after round of tear gas, rubber bullets and water cannons.

Photos appeared to show police snipers set up on neighboring buildings.

In a statement, the force said that a “large gang of rioters” had hurled petrol bombs at police and “set objects ablaze.” “At around 5.30 a.m., police (continued) to conduct (a) dispersal and arrest operation,” the statement added. “Meanwhile, rioters gathering inside the campus set fire and caused extensive damage.”

Protesters began leaving the campus on Monday morning, and large numbers could be seen making a break for it. Some were pushed back, however, after police fired tear gas and expanded their cordon. Earlier, protesters had said those attempting to leave were being arrested, and complained that they were being boxed in by the authorities.

Those still stuck inside said the atmosphere was growing increasingly desperate. Over Monday night, a group of government employees were sent to the campus to help underage protesters leave. A Facebook statement by Hong Kong police said that the “social workers will also look after their welfare and keep them company during further investigation in Police stations.”

“Of course, we want to leave,” a 23-year-old protester told CNN by phone from inside PolyU. “We are still quite safe currently in the campus, but if we try to leave … they will arrest us. They are just everywhere surrounding campus.”

The protester was not hurt but said he is “worrying about how to tell my parents” who don’t know he is inside the university. His parents think he stayed at his girlfriend’s house.

“We might have to wait for a lot of time,” he said, because he thinks the police strategy is shutting down the road for a few days so they can trap and eventually arrest everyone inside. “Currently, around me we just want to escape, we don’t have any equipment to help us fight.”

He later escaped with his girlfriend, after hiding under a bridge and sprinting to safety. He knows about 50 people who also got out, some of whom escaped by abseiling down a rope to waiting motorbikes or running along train tracks.

“You will never prepare for being arrested until you have to face it. Early in the revolution, everyone said we had to be prepared for being arrested, but you never think about it properly until it nearly happens to you,” he said.

Photos sent to CNN from inside the campus show what appeared to be a makeshift bomb made from a gas canister with bolts attached.

CNN cannot confirm that it is in fact a viable explosive device, or that it still contains volatile gas. A police spokesman said that gas canisters have been used during protests as weapons against them.

Disaster scene

Protesters have increasingly switched to using a form of napalm rather than just petrol bombs. Even though the substance is typically associated with military action – particularly US bombing during the Vietnam War – napalm is easily created from petrol and household materials, and recipes for doing so have been circulating among protesters since at least last week.

In a statement, PolyU management said “dangerous chemicals” had been stolen from laboratories and condemned the protesters’ “illegal acts and violence” in the campus, which they said had “been widely damaged.”

“We understand that students care about the current social situation, however, they must be calm and rational when fighting for anything,” the statement said. “Resorting to violence or other radical acts will not help solve the problem.”

When CNN visited the campus on Friday, students had built brick walls and set up security checkpoints around the entrances, as others stockpiled petrol bombs, other weapons, and food and water.

By Monday, there were shocking scenes of destruction in and around the PolyU campus, with barricades, bricks, debris and umbrellas strewn everywhere. At dawn, an enormous cloud of smoke hung over the area, from a large fire set near the entrance to the university. Other fires were set on a key bridge leading to campus, where protesters threw petrol bombs at police vehicles, succeeding in setting one of them on fire and forcing it to retreat.

Fires burn at the steps to Hong Kong Polytechnic University as police storm the campus early Monday.

Six months of chaos

The demonstrations began in June over a controversial China extradition bill, which sparked huge marches across the city.

The government suspended but did not immediately withdraw the bill. By the time the bill was withdrawn – three months later – the movement’s focus had already expanded to focus on complaints of police brutality and wider calls for democracy.

Escalating protests last week after the death of the HKUST student saw a traffic police officer shoot a protester during a clash in the early hours of November 11, and a man set on fire after he argued with protesters. A 70-year-old man died after being struck on the head with a brick during a clash with protesters. Police said they were treating that case as a murder investigation.

With both the government and protesters refusing to back down, there is no immediate end in sight to the unrest.

Attempts to create a venue for dialog or even background talks have so far failed to get off the ground, hampered in part by the leaderless nature of the protest movement, which makes it difficult to say who, if anyone, could take part in negotiations with the government.

On Monday, Hong Kong’s High Court struck down a controversial mask ban which the government introduced in the apparent hope that making face coverings illegal would help reign in the protests. In the end, the move only further infuriated protesters, and the court ruled that the provision of a colonial-era emergency law it was enacted under was unconstitutional.

Last week, Chinese President Xi Jinping made rare public comments on the demonstrations, saying that “radical” protesters had trampled the city’s rule of law and that “stopping the violence and restoring order” was Hong Kong’s most “urgent task.”

CNN’s Jo Shelley, Jessie Yeung, Isaac Yee and Joshua Berlinger contributed reporting.