The provincial government's plans to develop Quebec's north have been the subject of controversy since they were unveiled by Jean Charest's Liberal government in 2011.
On Friday, about 200 demonstraters gathered in Montreal's financial district to protest .
Police ordered the crowds to disperse early in the afternoon after at least three patrol cars were vandalized.
Montreal police Sgt. Laurent Gingras said protesters also sprayed graffiti and broke a window at the Palais des Congrès.