Many Chinese mainland students at universities in Hong Kong have "fled" to neighboring Shenzhen or returned home, after rioters targeted major campuses amid the escalation of violent protests.

The students－some of them 19 and in their first year in the city－told China Daily on Wednesday that they feared the rioters' reckless assaults and bullying against people from the Chinese mainland.

During a forum between students and the president of the Hong Kong University of Science and Technology, a group of masked protesters attacked a PhD student, surnamed Zheng, from the Chinese mainland.

Similar violence was reported at the Chinese University of Hong Kong.

Since Monday, rioters have been vandalizing facilities and setting fires at major universities across the city. They brutally attacked people with different views in or outside the campus, with one victim being set on fire.

The violence escalated on Tuesday night. Rioters at CUHK hurled heavy objects and gasoline bombs from a footbridge outside the campus onto the Tolo Highway, a main thoroughfare in the New Territories, jeopardizing the safety of motorists and commuters.

The protesters clashed with the police, set fires and vandalized facilities in the nearby subway station. The violence forced the closure of the station and subsequently isolated the campus by cutting off transportation links for the students.

Various organizations from Hong Kong and neighboring Shenzhen helped the students, arranging buses and private cars to help transfer those affected across to the Chinese mainland. Some youth hostels in Shenzhen also offered free accommodation for the students.

Alice Lu, a master's program student at Hong Kong Baptist University, left the city through high-speed rail on Wednesday. Lu said her classes had been suspended for three days amid the chaos and she felt that her personal safety was threatened, especially with mainland students being attacked on campuses.

"I want to leave here as soon as possible," Lu said. "I feel like I'm living in a war zone … I'm very tired physically and mentally. What upsets me the most is why innocent people have to suffer all of this."

Celina Sang, a 19-year-old freshman at the City University of Hong Kong, told China Daily that she was frightened by what was happening on campus. She also heard people saying that some rioters had even entered university dormitories with lists of mainland students targeted.

Sang said her roommates had already left in panic. She herself left Hong Kong on a flight on Wednesday morning, without knowing when she would return to the city.

Sergey Lukanin, director of the Institute of Far East Studies at the Russian Academy of Sciences, said the violence has endangered the safety and stability of Hong Kong. "We can see some of the riots have funding support from overseas," he said.

"Many Hong Kong youngsters have been hoodwinked by people with ulterior motives, and those who want to ruin social stability will be punished eventually," he said.

Linda Yin-nor Tjia, assistant professor at the Department of Asian and International Studies at the City University of Hong Kong, said it was chaos at her campus. Tjia said classes have been suspended since Nov 11 and she herself opted to stay home as subway stations were vandalized.

Tjia said most of her graduate students are from the mainland.

"We have a group WeChat account and some of them told me that they went home (because of the escalating violence)."