Education-sector lawmaker Ip Kin-yuen said on Wednesday that the police decision to move on to the Chinese University campus in Sha Tin the previous day had made things worse.
Protesters hurled scores of petrol bombs while police fired back with water cannon and tear gas.
Police were at the university after students threw objects onto Tolo Highway and onto MTR train tracks.
"It's really sad and I think many people are angry as well. It is difficult to imagine that there is an attack on the university campus by police happening in Hong Kong," said Ip, who's the vice president of the Professional Teachers' Union.
He compared it to police actions against students in South Korea in recent decades, saying they were "provoking a lot of hatred in the campus - not only the students, but also the alumni".