Hong Kong, Nov 18 (IANS): Masked protesters attempted to escape from a Hong Kong university campus where they have been battling police on Monday, but were forced to retreat as officers fired tear gas at several locations.

The two sides have been involved in an increasingly intense conflict at Polytechnic University since Sunday, with the protesters shooting police with arrows, using catapults to launch rockets and petrol bombs, and setting fire to buildings and bridges, reports the South China Morning Post.

Following a day of fierce battles, police on Sunday ordered everyone to leave the varsity campus or risk "taking part in a riot", an offence punishable by 10 years in prison.

They also warned rioters to stop using petrol bombs, arrows, cars or other lethal weapons to attack police, or officers would use "minimum force", including live rounds, in response.

But dozens of people who left, including first aiders, were immediately arrested.

On Monday morning, some managed to escape at around 8 a.m., but others were forced back into the campus buildings.

Police sealed off key roads and approaches to the university, preventing anyone from going in or out.

At the nearby Urban Council Centenary Garden, riot police repeatedly dispersed and ran after onlookers who refused to leave and pepper sprayed those that did not move.

At least seven people were detained and led away by police, with a least one suffering a head injury.

In a separate development, the police confirmed that three live rounds had been fired in Tsim Sha Tsui area at around 3 a.m. on Monday when a "mob of rioters" assaulted officers and helped a 20-year old Chinese female protester escape custody.

Meanwhile, protesters pledged to continue their strategy of bringing the city to a partial standstill on Monday morning by blocking major thoroughfares and disrupting public transport services in a bid to divert police manpower.

Some also responded to calls to rescue their peers in the Polytechnic University.