Riot Police Storm Hong Kong Uni Campus, Arresting Students Barricaded Inside

'Thousands' of Hong Kong university students have barricaded themselves in a building and stockpiled petrol bombs, bricks and other weapons, setting fires as police storm the campus.

Police on Monday afternoon (AEST) stormed into the Hong Kong Polytechnic University, using tear gas and batons to arrest those who had been holed up inside after they tried to escape from the buildings.

Media at the scene reported more than 100 people were arrested, detained on the street with their hands restrained with plastic zip ties.

Policemen in riot gear detain a protester who was trying to flee from the Hong Kong Polytechnic University. Image: Getty

It came after an all-night siege that included firing repeated barrages of tear gas and water cannons, and police reportedly firing live rounds. It was also just hours after Hong Kong's high court struck down a government ban on face masks, imposed as an emergency regulation in response to the protests, ruling the ban was unconstitutional.

The university's student union claimed "thousands" of people were still inside the campus, with "numerous" injured.

Protesters watch as a fire burns at the main entrance of Hong Kong Polytechnic University on Monday. Image: Getty

"Of the seriously injured, three persons have suffered injuries to their eyes and around 40 persons are experiencing hypothermia due to being directly hit by police water cannons," the student union said in a Facebook post.

"Because most of the emergency relief team and first-aiders have been arrested and taken away, there are insufficient resources and personnel within campus to treat the injured."

Officers threatened to use live rounds to break up the protests, and have reportedly arrested dozens of unarmed civilians who arrived in the area on Monday morning to call for the siege to end.

Live rounds were reportedly discharged as protesters surrounded an ambulance with two officers inside.

Anti-government protesters flee after clashing with police at Hong Kong Polytechnic University on Monday. Image: AAP

On Monday afternoon (AEST), the protesters tried to make a break, emerging from the buildings in force. However, police used tear gas and batons to meet the protesters, making many arrests.

Anti-government protesters had barricaded themselves inside the university for several days, fighting back with petrol bombs and bows and arrows.

Earlier in the day, protesters used bows and arrows, and one arrow struck a media liaison officer in the calf. Photos on the department's Facebook page show the arrow sticking out of the back of the officer's leg.

As riot police moved in from all sides, some protesters retreated inside the university. Others set fires on bridges leading to it.



Hong Kong Police Threaten Live Rounds After Officer Struck With Arrow

Hong Kong police have threatened to fire live bullets if "rioters" did not stop using lethal weapons in the latest flare up during anti-government protests that have convulsed the Chinese-ruled city for five months.

A huge blaze burned along much of a long footbridge that connects a train station to the campus over the approach to the Cross-Harbour Tunnel, a major road under Hong Kong's harbour that has been blocked by the protesters for days.

The use of bows and arrows and catapult-launched petrol bombs threatened to escalate the violence in the more than five-month anti-government movement.

A protester attempts to extinguish a fire at the entrance of the uni. Image: Getty

Activists saw it as an erosion of Hong Kong's autonomy under the "one country, two systems" formula implemented in 1997 when Britain returned the territory to China.

The bill has been withdrawn, but the protests have expanded into a wider resistance movement against what is perceived as the growing control of Hong Kong by Communist China, along with calls for full democracy for the territory.

Image: Getty

With AAP.