Fierce clashes erupted on Monday lunchtime as a group of protesters made another desperate attempt to flee Polytechnic University which has been surrounded by the police since the weekend.

Violent and chaotic scenes broke out, with the police catching some people, and members of both sides falling down among the piles of bricks and other debris in the road.

Officers battered some of their captives with batons and dragged some along the ground, while service revolvers were pulled out at one point. Some of those detained were covered in blood.

Other protesters had earlier blocked roads in Tsim Sha Tsui in a bid to divert police attention away from the embattled university campus in nearby Hung Hom.

A crowd tried to advance on the university from Jordan, throwing Molotov cocktails towards officers who were blasting them with tear gas.

The protesters formed human chains to pass items such as umbrellas to their frontline, shouting "We’re here to save PolyU protesters."

Across the city, people were anxiously watching the events unfolding on TV, with growing fears that the siege of PolyU would end in a bloody crackdown.

The police had earlier made a fresh appeal to those inside the uni campus to leave, saying they should throw down their weapons, remove their gas masks, and make their way out via the Cheong Wan Road South Bridge.

The police said they were using "the minimum force necessary" to handle protesters who they said were "charging" at officers.