Riot police have turned Hong Kong university campuses into battlegrounds, firing rounds of tear gas at protesters and bringing the city to the 'brink of total breakdown'.
The clashes came a day after police shot a protester at close range and a man was doused with petrol and set on fire in some of the worst violence in the former British colony in decades.
University students were called on to boycott classes as part of a citywide strike, while white collar workers were told to skip work and business owners to close their shops.
Footage has emerged of running riot police firing tear gas and less-lethal projectiles into a sports ground as protesters run for shelter at Chinese University of Hong Kong.
Protesters are seen shielding themselves with umbrellas and rubbish bins to stay safe.
Students and alumni have been forced to form a human chain to move to the front line of the conflict between protesters and police.
"Our society has been pushed to the brink of a total breakdown," a police spokesman told a briefing.
Police also fired tear gas at City University in Kowloon Tong, beneath the Lion Rock, and at Chinese University on the other side of the mountain, where protesters threw petrol bombs and bricks at police.
Protesters at City University have stockpiled bricks and petrol bombs on the bridges and other approaches and were making small devices with nails to apparently puncture tyres.
Streets inside and outside the Chinese University campus entrance were littered with bricks, other debris and small street fires as police tackled some protesters to the ground.
A van used as part of a street barricade was set ablaze.
Huge plume of smokes emerged from the campus can be seen from across the Tolo Harbour as web users described it as 'chaos' and 'apocalypse'.
The university said some people had broken into a storeroom and taken bows, arrows and javelins that were later retrieved.
"It's crazy that police have been firing tear gas for more than 20 minutes. If they didn't come in, we wouldn't clash with them. It's our school. We need to protect our home," Candy, 20, a student, told Reuters.
Several people were wounded, including a student reporter hit in the eye, apparently by a brick, who was sitting in tears as friends offered comfort.
Another clip shows first-aid responders carrying injured students to safety for medical treatment.
Tuan Sung-chi, vice chancellor of the Chinese University of Hong Kong, arrived the scene in the afternoon as he tried to negotiate with the police.
The police claimed they responded to an incident regarding people hurling objects onto railway tracks at nearby University station and did not intend to enter the campus, reported hkon.cc.
Hong Kong leader Carrie Lam said protesters were being extremely selfish and hoped that universities and schools would urge students not to take part in the demonstrations.
More than 260 people were arrested on Monday, police said, bringing the total number to more than 3,000 since the protests escalated in June.
Protesters are angry about what they see as police brutality and meddling by Beijing in the freedoms guaranteed under the "one country, two systems" formula put in place when the territory returned to China from British rule in 1997.
