Protesters in Hong Kong have battled police on multiple fronts, from major disruptions during the morning rush hour to a late-night stand-off at a prominent university, as the five-month anti-government movement took an increasingly violent turn.

Petrol bombs and fires lit up the night at the Chinese University of Hong Kong, while police massed for a possible clearing action with a water cannon.

It was the second straight day of weekday protests and followed an especially violent day on Monday when police shot one protester and a man was set on fire.

Tuesday began with protesters shutting down parts of the commuter rail system and blocking roads. Bus tyres were punctured and debris thrown on railway tracks.

Police fired tear gas at protesters who littered roadways with bricks and anything else they could get their hands on — even merchandise still wrapped in plastic and tossed out from boxes.

Hong Kong leader Carrie Lam, speaking to news media after a weekly meeting with advisers, called the blocking of the morning commute “a very selfish act”.

Students targeted with tear gas
Students targeted with tear gas (Kin Cheung/AP)

“People from different sectors in society are holding fast to their positions and refusing to concede to violence or other radical actions,” she said. “I hereby express my gratitude to those who are still going to work and school today.”

Many office workers turned out in support of the protesters, who rallied for a second day on Pedder Street in Central, a business and high-end shopping district.

A few thousand people took over several blocks, chanting “Five demands, not one less” while holding up one hand with five outstretched fingers.

Office workers hold up their hands to represent their five demands
Protesters hold up their hands to represent their five demands (Vincent Yu/AP)

Their demands include democratic changes and an independent investigation of police treatment of protesters.

Traffic was blocked on two major roads, with buses and half a dozen of Hong Kong’s famous trams lined up unable to move.

The words “Join Us” were spray painted on the front window of a halted double-decker bus abandoned by the driver and passengers.

Office workers filled the pavements and overhead walkways, some joining the protesters in chanting.

Hong Kong Protests
Office workers join the protest (Vincent Yu/AP)

Police fired tear gas to disperse protesters and onlookers who were hurling abuse at the officers. At least one person was injured when he was struck on the head by a tear gas canister, but protesters returned by evening and were again blocking roads with bricks and commandeered buses.

Protests ebbed and flowed all day at several universities. Classes were cancelled and clashes were particularly intense at the Chinese University of Hong Kong.

Scores of officers charged on to the campus after firing tear gas, arresting student protesters who tried to block their way with makeshift barricades, including a burning car.

That did not end the stand-off, which was continuing on Tuesday night.

Medical workers move an injured student
Medical workers move an injured student (Kin Cheung/AP)

Recent weeks have been marked by escalating vandalism of shops linked to mainland China and train stations, and assaults by protesters and pro-Beijing supporters.

On Monday, a police officer drew his gun during a struggle with protesters, shooting one in the abdomen. In another neighbourhood, a 57-year-old man was set on fire after an apparent argument.

Both remained in hospital on Tuesday, the shot protester in serious condition and the man who was burned in critical condition, the Hospital Authority said.