At least six people were arrested ahead of the annual anti-police brutality march in Montreal Tuesday, a yearly event traditionally marked by vandalism and violence.

Hundreds of people showed up to take part in the procession, which started late because of the arrest of at least six people.

The march wound its way across Ontario Street and up St-Denis Street, where some participants were quick to smash bottles and windows, including a front pane at a Gap outlet.

The rowdy crowd chanted and waved placards, but were clearly outnumbered by police officers in riot gear, said reporter Jay Turnbull, who followed the protest as it wound its way north.

Police used several "crowd control" techniques to keep the situation contained, said Montreal police Sgt. Ian Lafrenière.

Officers detonated stun grenades, which emit grey smoke and high-pitched noise.

The crowd stalled and thinned out as it reached Marie-Anne Street, just south of Mont-Royal Avenue. Officers surrounded about 60 remaining protesters just after 9 p.m.

Police used Twitter to send regular updates on the protest.

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Montreal police make their way around an overturned burning trailer during last year's anti-police brutality protest. ((Patrick Sanfaçon/Montreal La Presse/Canadian Press))

Authorities issued several warnings to the public to avoid the march area, notably around Place des Festivals, an outdoor area located at the intersection of de Maisonneuve West and Jeanne Mance Street. 

Chief Insp. Sylvain Lemay took the extraordinary step Tuesday morning of warning people who live and work in the area to stay away, saying the demonstration has a history of vandalism and violence

"We invite people either to finish earlier or use another [route] to go back home," he said. "That's going to prevent them from getting in the middle of this protest and to go home safer."

Lemay said part of the problem is that organizers refuse to get a legal permit.

This year marks the 15th annual protest and as in previous years, organizers refused to disclose their planned route to police.

Sophie Sénécal, spokeswoman for the Collective Opposed to Police Brutality, said her group doesn't reveal its plans beforehand because police have historically made pre-emptive arrests in an attempt to quash the protest before it starts.

She said organizers encourage the protesters to be smart and safe, and she accused police of mounting a fear campaign against the demonstrators.

She said her group is marching to denounce police and the City of Montreal for routinely ignoring decisions by the Quebec Human Rights Tribunal that find police guilty of harrassment and racial profiling.

Last year, the protest started peacefully but escalated after some people threw beer bottles at police and lobbed firecrackers at their patrol horses.

A riot squad called in to quell the crowd arrested several people who were accused of assembling illegally, vandalism, assault and armed assault.