HONG KONG (AP) — Police fired tear gas at protesters who littered streets with bricks and disrupted morning commutes and lunch breaks Tuesday after an especially violent day in Hong Kong's five months of anti-government demonstrations.

Protesters and police using tear gas faced off in and around university campuses, where classes were cancelled in morning clashes. Commuter train passengers were escorted along the tracks and subways were shut amid transit disruptions.

A few thousand protesters took over several blocks in the central business district at lunch time, facing off briefly with a police contingent that threatened to use tear gas but then retreated out of sight.

The demonstrators chanted "Five demands, not one less" holding up one hand with five outstretched fingers.

Traffic was blocked on two major roads by the crowds, with half a dozen of Hong Kong's famous trams lined up unable to move. The words "Join Us" we're spray painted on the front window of a stopped double-decker bus abandoned by the driver and passengers and one of its windows was broken.

Office workers filled the sidewalks and overhead walkways to watch the action, with some joining the protesters in chanting.

One 24-year-old, who would not give his name, said he was there to support the protesters and accused the police of using excessive force, a common complaint among the city's 7.4 million people.

Recent weeks have been marked by escalating vandalism against shops and train stations and assaults by both protesters and pro-Beijing supporters on the other side.

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."

"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."

On Monday, a police officer drew his gun during a struggle with protesters, shooting one in the abdomen. In another neighborhood, a person was set on fire after an apparent argument. The Hong Kong hospital authority said both were in critical condition. Video of another incident showed a policeman on a motorcycle riding through a group of protesters in an apparent attempt to disperse them.

Police say those events are being investigated but defend the officers' actions as necessary for their own safety.

Lam pledged Monday to stop the violent protests in comments suggesting harsher legal and police measures could be coming.

"I do not want to go into details, but I just want to make it very clear that we will spare no effort in finding ways and means that could end the violence in Hong Kong as soon as possible," she said.

Lam refused to accept the demands for political concessions. "These rioters' actions have far exceeded their demands, and they are enemies of the people," she said.

One of their five demands is for the government to stop labeling the demonstrators as rioters, which connotes that even peaceful protest is a criminal activity. Their other unmet demands are for democratic changes in Hong Kong's government, criminal cases to be dropped against protesters, and for police actions against the protesters to be independently investigated.

In Washington, the U.S. government said it is watching the situation with "grave concern."

"?We condemn violence on all sides, extend our sympathies to victims of violence regardless of their political inclinations, and call for all parties — police and protestors — to exercise restraint," State Department spokeswoman Morgan Ortagus said in a statement.

She urged the government to address the underlying concerns behind the protests and the protesters to respond to efforts at dialogue.

Police said they arrested more than 260 people on Monday, raising to 3,560 the number of arrests since the movement erupted in June.

The protests initially began over a proposed law that would have allowed criminal suspects to be extradited to mainland China, where they could face opaque and politically sensitive trials. Activists saw the bill as another sign of an erosion in Hong Kong's autonomy and civic freedoms, which China promised would be maintained for 50 years under a "one nation, two systems" principle when the former British colony returned to Chinese control in 1997.

Lam eventually withdrew the extradition bill but has insisted the violence stop before any further political dialogue can take place.

District council elections on Nov. 24 are seen as a measure of public sentiment toward Hong Kong's government. Pro-democracy lawmakers have accused the government of trying to provoke violence to justify canceling or postponing the vote.

Copyright 2019 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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