Paint was splashed and anti-Plan Nord posters were pasted to the windows of the Montreal convention centre overnight ahead of the Board of Trade's Strategic Forum on Natural Resources.
"Non Plan Mort" — or "No to Plan Death" — was also sprayed on the windows.
Plan Nord is the provincial government's plan to develop natural resources in Quebec's north.
A demonstration was set to take place before the 7:30 a.m. convening of the forum on natural resources.
Of the dozen or so protesters, three have been detained by police for disturbing the peace.