MONTREAL -- While most Quebec students return to school this week, a hard core of strikers at two French universities continue to boycott classes, heckling and blockading any classmates who oppose them.

The University of Quebec at Montreal (UQAM), a sprawling university in the centre of the city, has filed a police complaint against several student groups following two days of disruptions.

The school said in a statement that the complaint follows "acts of intimidation and disruptions committed (Tuesday) by demonstrators."

UQAM says classes in eight different campus buildings have been hit by blockades.

The move didn't stop mask-wearing protesters from occupying a psychology class at UQAM on Wednesday. Video taken by a student shows the demonstrators flipping the lights off and on, heckling students and banging on desks.

One young woman said the blockaders had stopped people from entering the class before letting them pass. But she said they returned 30 minutes later.

"There were 40 of them," said the woman, who gave her name as Sophie. "They were anything but peaceful, even aggressive, they spoke to us about two inches from our face, quite intimidating."

Premier Jean Charest introduced a special law in May that suspended the spring semester until this week and cracked down on student groups that encourage violence.

Post-secondary students across Quebec voted to return to class this week but students in several programs at UQAM and the University of Montreal remain on strike. The holdouts have blocked access to classrooms and chased students and professors out of class.

Riot police were called to the University of Montreal campus Tuesday after campus security guards were assaulted and a building was vandalized. Sixteen people were arrested.

A day earlier, police took 20 people into custody at the University of Montreal after protesters barricaded themselves inside a classroom.

About a third of Quebec post-secondary students went on strike on Feb. 14 to contest a tuition hike that amounts to $1,800 per student over seven years.

The conflict was marred by window-smashing rampages and violent clashes between police and protesters that led to thousands of arrests and made international headlines.