A small group of Quebec nationalists was pelted with rocks and beer bottles in Montreal on Saturday by another group that took issue with its message.
Montreal police spokesman Dany Richer said about 30 protesters were taking part in a peaceful rally in a downtown street corner shortly after noon when the confrontation took place.
Some 15 people, described variously as anarchists and anti-fascists, threw a variety of objects at the protesters and the police officers monitoring the protest, Mr. Richer said.
No injuries were reported, though Mr. Richer said the windows of both a nearby building and a city bus were broken during the 15 minute showdown.
Ten people were taken into custody to be interrogated, though police hadn't laid any charges by Saturday evening.
The nationalist protest was planned and organized by a group called the Legion Nationale, police said.
The group describes itself on its website as being devoted to preserving and protecting Quebec's culture, values and moral principles.
"The decadence and degeneration that is darkening our lives will lead us little by little, if nothing changes, to our own destruction," the website says.
The website is written partly in a German-style font and the group's coat of arms shows two white hands clasped together over a black and red backdrop.
The Legion Nationale outlines a strict policy of non-violence on its website, stressing that anyone who doesn't comply will be banned from the group.
At the protest, members stood on the sidewalk of a busy downtown street waving Quebec flags at passersby.
Police were trying to determine Saturday whether those who challenged the protesters belonged to a particular group or movement.
Mr. Richer said there was no connection between the incident and the Occupy Montreal, which held a peaceful rally at its former encampment on Saturday.
The Occupy camp, which was dismantled by police on Friday, was only a few blocks from where the clash occurred.
By 2 p.m., the busy downtown corner showed little sign of the conflict, except for a few broken beer bottles and rocks strewn along the sidewalk.
A worker at a nearby hotel said the incident was over quickly and caused only a small disruption.