HONG KONG — Mainland Chinese students have begun fleeing Hong Kong campuses over security fears, police and university officials said on Wednesday, as the city's seething political crisis saw some of its worst violence this week.

The most intense clashes on Tuesday occurred at the Chinese University of Hong Kong, where pitched battles were fought with the police firing tear gas, water cannon and rubber bullets and protesters throwing petrol bombs and bricks, paralyzing the campus and the area around it.

A group of mainland students at CUHK attempted to depart the campus on Wednesday morning over safety concerns but had to be shuttled away by a police boat because they were unable to leave via obstructed roads.

"The police decided to deploy a police launch to assist the group of students to go to a safe location," the force said.

Images on local outlet Stand News showed dozens of people — some carrying luggage — standing next to a vessel with police markings, purportedly fleeing the campus.

The Hong Kong University of Science and Technology meanwhile arranged a special bus service to ferry students from its campus to a station that offers services to the mainland.

"While we are not aware of any imminent threat to campus safety, we understand some staff and students have the desire to leave campus," the university said in an email to students.

The Hong Kong Baptist University suspended on-campus teaching two weeks before the scheduled end of the semester, switching to either online sessions or postponing classes altogether. It also announced online teaching arrangements for students who choose to return to mainland China.

CUHK later announced it too was ending the current term early because of the unrest.

It was not immediately clear how many mainland Chinese students have left Hong Kong during the latest escalation of violence.

A youth wing of the Communist Party in Shenzhen on Wednesday said it was offering free accommodation at its facilities for mainlanders studying in Hong Kong. Other groups posted similar offers on Weibo, China's Twitter-like social media platform.

Separately, the Taiwanese government said it was making arrangements to help Taiwanese students in Hong Kong return home. The island's Mainland Affairs Council said 280 students were expected to return home on Wednesday and Thursday.

The protest movement is the biggest challenge to Beijing's rule since Hong Kong was returned by Britain in 1997, fueled by fears that China is choking the liberties and freedoms the city is meant to have under the handover deal.

More radical demonstrators have targeted businesses and people perceived to be pro-China. In a particularly shocking incident, a man was doused in a flammable liquid and set on fire during an argument with pro-democracy protesters.

Such attacks have been picked up by Chinese state media, which have described the pro-democracy protesters as "rioters".

The nationalist tabloid Global Times described the situation as an "Escape Day".

"It's hard to go to the campus, it's risky," said a Hong Kong University postgraduate student who gave his surname Zhang.

"The atmosphere is pretty intense. I live in (a) student flat and so far it's fine. But I'm afraid if anything happened, you can't leave."

Another mainland student who asked to remain anonymous said she recognized many other students at the West Kowloon high-speed railway station, which connects Hong Kong with Shenzhen and beyond.

"The atmosphere these days... makes me want to leave," she said before departing for the mainland, referring to the "bad mood" the situation had caused among Chinese students.

The only thing that made her feel better was "going to McDonald's".

"I can't stand that," she said. "So I finally left." — AFP