A fifth suspect wanted in connection with a clash with security guards at a Chinese University entrance this month has turned himself in.

That came after raids by the police Monday evening on multiple locations at the university that saw three students arrested on top of one more student, 20, caught on the day of the incident.

The fifth suspect, 22, surrendered at Tsuen Wan police station around 5pm yesterday, sources said.

He was arrested for unlawful assembly and assault with intent to cause certain acts to be done or omitted.

That came soon after New Territories south regional superintendent Chan Chi-cheong appealed to the suspect and others to turn themselves in.

"I hope they can assist in our inquiry by surrendering themselves to justice so that their teachers, families and schoolmates would not breach the law inadvertently for harboring them," Chan said.

Chan, a CUHK alumnus himself, slammed the student union for understating the attack.

"The melee was merely described as a clash between guards and students by the union," Chan said.

"I greatly condemn such a despicable act and shameless quibble The suspects had in fact inflicted triad-style bullying and violence against those guards."

He said the attack was believed to be triggered by discontent over students having to present student cards to security guards when entering the campus.

On Monday evening, three suspects, all students aged between 19 and 22, were arrested in Sha Tin, Fan Ling and Tsuen Wan over the same charges.

Owen Au Cheuk-hei - a former student union president and the current president of its provisional executive committee - was among those arrested. They were detained at three police stations as of yesterday.

In a video released by the university's CUHK Campus Radio on Monday, Au, 22, was seen being taken away in a police car from the student dormitory of the university's SH Ho College.

The police were also seen in the corridor of student dormitories at the university's Lee Woo Sing College as well as Wu Yee Sun College, during which some students demanded to see the college's housekeeper.

Au's fellow committee member, Anson Yip Tsz-yuen, said Au reported to Sha Tin police station on Monday, but was then arrested there.

In a statement released on Monday, the student union said police raided at least three places: SH Ho, Lee Woo Sing and Wu Yee Sun colleges.

"The union expresses regret over the arrests of CUHK students and condemns the university for refusing to handle issues related to the university's security," it said.

The attack took place on January 11, when eight masked and black-clad individuals told students not to present cards to guards, who were then spattered with suspicious white powder during a melee.

Owen Au being taken away. Above left: Chan Chi-cheong.

Fifth student surrenders as uni raids slammed