Quebec's student tuition protest turned violent again Friday as a group of vandals smashed windows and trashed the Montreal office of the education minister.

Seven people were arrested in the melee.

Police say about 15 people charged the office of Line Beauchamp's in her Bourassa-Sauve riding Friday morning and did the damage before returning to a group of about 40 other students nearby.

The vandalism comes a day after provincial police arrested a man for allegedly threatening a Quebec cabinet minister.

Two other investigations are underway involving alleged threats against two ministers, but police refuse to name them.

But some reports have identified them as Beauchamp and Justice Minister Jean-Marc Fournier.

The University of Montreal was also in court Friday seeking an injunction after several hundred students stormed the institution Thursday and caused extensive damage inside.

That attack occurred even though the university had a previous injunction preventing protesters from blocking access to the building, CTV Montreal's Stephane Giroux reported Friday.

Lawyers for the university were back in court attempting to get a more wide-ranging injunction, he said.

"That debate was going on all morning and the injunction goes as far as requesting that not one single student be allowed to demonstrate within 25 metres of the university and they don't interfere with anyone trying to get in," Giroux said.

Student associations and even some teachers were in court fighting the injunction, arguing it violates freedom of speech laws, he said.