HONG KONG (AP) — Police increased security around Hong Kong and its university campuses Wednesday as they braced for more violence after sharp clashes overnight with anti-government protesters.

Many subway and rail stations were closed for the morning commute as protesters blocked train doors from closing and vandalized train cars. Classes were suspended at universities, and parents of school students were advised they could keep their children home.

Police subdued a few protesters as a crowd gathered for a third straight day in a central business and high-end retail district, public broadcaster RTHK reported. Both protesters and police remained in the area, and office workers watched from the sidewalks.

Farther afield, students and others at the Chinese University of Hong Kong hunkered down for another possible clash with police. Gasoline bombs and fires lit up parts of the campus the previous night, as police battled back with tear gas and rubber bullets.

Security Secretary John Lee said the use of force was needed to gain control of a bridge from which protesters were dropping objects onto a roadway below.

"The police have a duty to ensure public safety is maintained," he told reporters. "That's why we had to take charge of the bridge formerly controlled by the protesters."

Before the evening violence, a police official warned protesters were carrying out "insane acts" and Hong Kong was on the brink of a total breakdown after more than five months of protests.

"Our society has been pushed to the brink of a total breakdown," Senior Police Superintendent Kong Wing-heung said late Tuesday.

He said Hong Kong's mass transit system and subway, known as MRT, was strained by violence and vandalism.

"Masked rioters have lost control and committed insane acts like throwing trash, bicycles and large objects onto MTR tracks, hanging trash on overhead power lines," he added.

Groups of riot police were deployed around central Hong Kong and its outlying territories to try and contain new violence. Many students at CUHK, in the outskirts of the sprawling metropolis, were armed with gasoline bombs while some carried bows and arrows.

The university's student union president, Jacky So, appealed for an injunction with the High Court to ban police from entering the campus without a warrant, or the school's approval. Police had entered the campus and fired tear gas and used a water cannon late Tuesday.

The injunction would also block police from using crowd control weapons, such as tear gas and rubber bullets at the university. A decision is expected late Wednesday.

The city's religious leaders appealed Wednesday for an end to the violence and called on both police and protesters to show restraint.

"At this very critical point, the people of Hong Kong must unite and say no to violence," said a statement issued by the leaders of Hong Kong's six major religious groups.

A statement from the Chinese government's liaison office in Hong Kong said that the semi-autonomous territory is "slipping into the abyss of terrorism." It called the setting of a man on fire an act of "flagrant terrorism."

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 who was defending China was set on fire after an apparent argument.

The man remained in critical condition Wednesday, and the protester was in serious condition, the Hospital Authority said.

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

Police have arrested more than 3,500 people since the movement began in June over a now-withdrawn extradition bill.

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.

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Associated Press writer Yanan Wang in Beijing contributed to this report.