Montreal police detained 19 protesters on the fourth floor of the Jean-Brillant building at University of Montreal on Monday, as riot police faced off against about 50 students who locked themselves in the building, ignoring warnings from police to vacate the premises.

The protests in support of continuing the Quebec student strike came as courses resumed at universities where the winter term was suspended.

Police, called in by University of Montreal administrators to take charge of the situation after emergency exits were blocked, removed those detained from the campus, then released them. The students could also face charges related to the protest.

Protesting students block access to a sexology class at UQAM. (Elias Abboud/CBC)

Police in vehicles were also patrolling, but not fully deployed, at UQAM, the University of Quebec's Montreal campus. There, dozens of demonstrators, many wearing bandanas on their faces, filed through classrooms clanging on pots, while others staged sit-ins in front of classroom doorways.

The protesters said they were only blocking classes attended by students from associations that voted in the past few weeks to continue the strike.

The university administration said in all, 60 classes were cancelled Monday morning — or about one-third of all classes.

One professor, in a psychology course, responded by locking the doors to keep out protesters and posting a security guard outside the classroom. But tens of other classes, mainly in arts and humanities, were cancelled by Monday at 9:30 a.m. ET.

Earlier in the morning, a contingent of college and university professors unveiled a banner at UQAM supporting the student cause.

Some students demonstrating inside UQAM buildings chanted: "Election: piège à cons" — "Elections: for fools" — a slogan borrowed from the 1968 student protests in France.

Bill 78 mandated return to classes

Most Quebec college and university students have voted to end their boycott of courses, but 9,000 largely humanities students at UQAM are still on strike, as are 2,800 at the University of Montreal.

The Quebec government officially suspended the winter term at many universities on May 18 due to the student crisis. Hundreds of courses had effectively shut down at that point, some since as early as February, because of the student boycott, campus pickets and professors' unwillingness to teach, either in solidarity with students or in the face of the workplace disruptions.

Under the government's contentious Bill 78, now known as Law 12, the semester was supposed to resume this week. Law 12 also makes it an offence to organize or participate in a protest "that could result in" a student being blocked from a classroom, where the demonstration is in or within 50 metres of a school building. It is also an offence to "contribute to slowing down, degrading or delaying" university or college classes.

Montreal police have said they won't enforce those provisions unless school authorities ask them to. Police said their deployment at the University of Montreal on Monday morning was to enforce the Criminal Code, not Law 12. Officials at UQAM said they would decide later Monday whether to request police enforcement of those provisions on their campus.

The head of the association representing university rectors across Quebec, Daniel Zizian, said universities would offer courses to students who showed up for class.

"As for students who don't show up, they run the risk of obtaining an incomplete or a failure on their transcript," Zizian added.

Quebec's still-simmering student crisis emerged from a host of concerns with the province's education system, including financial accessbility and the corporatization of campuses. But the spark for the province-wide protests that clogged streets and shut down classes last winter and spring was the Liberal government's plan to raise tuition by as much as 82 per cent over seven years.