According to Montreal police, the majority of people were arrested under municipal bylaw P-6, which makes it illegal to cover one's face while taking part in a protest and for failing to provide authorities with an itinerary.
In a tweet, authorities also said some people were arrested for breach of peace.
At least 150 people left the protest with a $637 fine because of their participation in the illegal event.
Though Montreal police have not yet confirmed the exact number of arrests, authorities were seen verifying the identities of about 100 people gathered on the corner of Sainte-Catherine and Sainte-Élisabeth streets.
Police officers also rounded up several groups and proceeded with mass arrests throughout the duration of the march.
Most of those taking part had formed smaller groups following police orders to disperse after the protest was declared illegal because organizers had failed to provide authorities with an itinerary.
Protesters had first gathered on the corner of Saint-Urbain and Ontario streets near police headquarters around 4 p.m., where they were met by groups of police officers who tried to get them to disperse.
2 officers taken to hospital
Two police officers were taken to hospital, according to Montreal police spokesman Laurent Gingras.
One of the officers had two broken teeth and another felt unwell.
Anticipating the worst, police say
Montreal police had been preparing for the worst in anticipation of the march. “We’re hoping for the best, but we’re getting ready for the worst,” said Montreal police Cmdr. Ian Lafrenière earlier today.
The demonstrations, which have been held in Montreal every March for the past 16 years, are meant to support International Day Against Police Brutality, but have been known to end with violence and mass arrests.
Last year's march saw 226 arrests.
Lafrenière said the reason for violence in recent years is partly due to fewer activists and more troublemakers hitting the streets.
“It looks like a sport now. Some people are coming to different protests because they want to have a good time,” he said.
Police took extra steps on Friday morning to warn the public, handing out flyers at downtown businesses and metro stations.
Authorities warned that large crowds could create issues for public transit, especially during the evening rush hour.