Montreal police moved quickly on Saturday to crack down on an annual protest that has a history of getting out of hand.
A crowd of demonstrators gathered outside a busy north-end subway station to denounce police brutality.
It was the same location where, this past January, an officer was captured on video telling a homeless man he would tie him to a pole for an hour in the freezing cold if his behaviour didn't improve. The officer was disciplined for his actions.
Organizers of Saturday's protest said they wanted to bring awareness to what they described as racial and social profiling, along the targeting of homeless people.
Adis Simidzija, a 25-year-old university student, said he's still upset about the way police handled the student marches during Quebec's so-called Maple Spring two years ago.
"We're here to protest against the police brutality we saw in the 2012 student protests, and that we see every year," Simidzija said.
But the demonstration didn't last long.
Using a loudspeaker, police declared it illegal within minutes because they weren't provided with an itinerary.
Helmeted officers on bikes and horseback, and later in riot gear, forced many of the protesters onto a side street and surrounded them.
Montreal police said late Saturday afternoon about 150 people were being detained under a municipal bylaw.
At least one person was injured in the protest, police said on Twitter.
Aside from a vandalized news truck belonging to CBC's French-language service, there were few signs of the troubles that have marked previous versions of the protest.
A demonstration against police brutality has been held in Montreal for the past 18 years. Many of them have ended in violent clashes between protesters and police.
More than 200 people were arrested at last year's protest, which was also cut short by police.
Felix Gamache, a 19-year-old college student, said he didn't even get a chance to join Saturday's demonstration.
Gamache and his friend arrived shortly after it began, at 3 p.m., and were cut off from other protesters by a line of police.
"I think, first of all, we have a basic right to protest," he said.