The scene in downtown Montreal was reminiscent of numerous street marches last year in which students resisted tuition hikes.
This time the protesters, who were smaller in number than at last year's huge marches, opposed current plans to extract resources in northern Quebec.
Many in the crowd of several dozen protesters wore the red squares associated with last year's student strikes. A number were masked.
There were clashes with police. Police said three cruisers were vandalized while riot cops chased away the demonstrators from a convention centre, eventually dispersing them.
They had been protesting at a job fair that was designed to promote opportunities in the natural resources sector.
Police declared the gathering illegal as soon as it began. Authorities said they did so because no route for the march had been given to police beforehand.
A small number of protesters, some carrying sticks and rocks, broke away from the main mob and moved toward the convention centre where the job fair was taking place. They pounded on the windows of the convention centre and someone began spray-painting the words, "Idle No More."
Police said the cruisers were damaged after the crowd was told to disperse.
The two-day convention is being sponsored by the Metropolitan Montreal Board of Trade. A news release said visitors would get a chance to network and discover job opportunities that would allow them to work in what was described as a "dynamic" sector.
Mining giant Rio Tinto Alcan, engineering firm SNC-Lavalin, and the pipeline company Enbridge were included on the list of oil, gas and mining companies taking part in the event.
Visitors were asked to bring a piece of ID with them.
One spokesman for the demonstrators said the jobs were being offered by corporations with no respect for people or the environment.
"They're digging open-pit mines where there were mountains before and they're clear-cutting where people are living," Yvan Bombardier said in an interview.
"By clear-cutting those forests, they're destroying the entire environment for wildlife, but also for the families that are living there."
Many of the demonstrators, who sported the familiar red square of last year's student protests, added a red feather to show support for the Idle No More aboriginal-protest movement.
One man who tried to force his way into the convention centre was stopped by police but was later released.
The job fair continues through Saturday.
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