HONG KONG (AP) -- Police and protesters battled outside university campuses and several thousand demonstrators blocked roads as they took over a central business district at lunchtime on Tuesday in another day of protest in Hong Kong.
The clashes followed an especially violent day in Hong Kong's five months of anti-government demonstrations, in which police shot one protester and a man was set on fire.
Protesters littered streets with bricks and disrupted train service during the morning rush hour on Tuesday. Commuter train passengers were escorted along the tracks, and subways were shut because of disruptions.
Police used tear gas in faceoffs with protesters in and around universities, where classes were canceled.
Following a standoff outside Chinese University, scores of officers charged onto the campus after firing tear gas, arresting student protesters who tried to block their way with makeshift barricades, including a burning car.
A few thousand protesters took over several blocks of the central business district at lunchtime. The demonstrators chanted "Five demands, not one less" holding up one hand with five outstretched fingers. Their demands include democratic changes and investigation of police treatment of protesters.
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" were spray painted on the front window of a halted 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 man, 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.
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.
Recent weeks have been marked by escalating vandalism against shops linked to mainland China and train stations, and assaults by both protesters and pro-Beijing supporters.
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 57-year-old man was set on fire after an apparent argument.
Both remained hospitalized Tuesday, the shot protester in serious condition and the man who was burned in critical condition, the Hospital Authority said.
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.
Police spokesman Kong Wing-cheung said the burning had been registered as a case of attempted murder and called on the public to provide information about the assailant.
"Hong Kong's rule of law has been pushed to the brink of total collapse," Kong said, calling those who defend or maintain ties with violent protesters "accomplices."
In Beijing, foreign ministry spokesman Geng Shuang lambasted the U.S. and Britain over statements of concern over the spike in violence.
"The United States and Britain pretend to be fair on this incident, but it only reveals how they confuse right and wrong and how hypocritical they are. And their verbal justice once again exposes their double standards and ulterior motives," Geng said at a daily briefing.
China accuses the U.S. and other foreign powers of fomenting and encouraging the protests.
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 protesters' demands. "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. They also want criminal cases to be dropped against protesters.
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 protesters --- 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 Hospital Authority said 128 people were taken to hospitals, with one in critical condition and five others in serious condition on Tuesday.
The protests 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.