MONTREAL--Police wasted little time Friday cracking down on an annual protest that has a history of getting rowdy, deploying charging squads of helmeted officers, cops on horseback and pepper spray to corral demonstrators.

Montreal police, who have been dealing with regular protests since student unrest last year, usually let peaceful marches proceed even if they have been declared illegal under municipal bylaws.

On Friday, police massed platoons of officers around their downtown headquarters -- which was the target of the annual rally against police brutality -- and had made their first arrest before the march even began.

Officers piled on one protester to catcalls from the crowd and quickly hustled him away. Once the march was declared illegal, other protesters were scooped from the mob and police tightened their cordon.

They stopped people and rooted through their bags and backpacks. Wedge formations were used to split the crowd into smaller groups and steer them off into side streets. Pockets were quickly dispersed and some areas were blocked off as people were herded along or rounded up.

By the end of the evening, 150 people had been detained and ticketed for violating municipal bylaws and four others had been arrested for criminal acts.

CTV Montreal prepared a map of the key events during the protest.

University student Dominique Cyr said he heard noise grenades go off close by as police dispersed the crowd. He ended up in a small peaceful group near the back of the march.

"We didn't see a lot of things," he said. "But in the beginning the police were very aggressive."

His friend Cynthia St-Germain said she saw demonstrators being roughly arrested and couldn't believe how many cops were on the scene.

"There's as many police officers as there are protesters," she said.

They both were at the rally because of what they had seen during last year's student protests, which were known as Quebec's Maple Spring.

"During the Maple Spring, I saw a lot of students beaten by the police," Cyr said. "I saw police hit the students with their motorcycles, a lot of things like that.

"It's horrible. It's a criminal act that the police are doing on the people and they must pay for their crimes."

There were some injuries on Friday, two of them to police officers. One cracked his teeth during the melee; another officer, feeling faint, was also taken to hospital.

Demonstrators have gathered in Montreal for the last 17 years to protest against police -- and 15 of those marches have seen violence.

This year's demonstration carried a uniquely bitter undertone after police and protesters clashed almost nightly during the so-called Maple Spring.

The events of last year remain hotly debated here, with many protesters arguing the worst violence at the student marches was committed by police -- not the demonstrators.

During Friday's protest, one man carried a sign that read "Officer 728 has a lot of friends," a reference to a Montreal police officer who was videotaped last year pepper-spraying a group of demonstrators that didn't appear to be a threat and who was later also investigated for excessive force.

Police swept down the sidewalks Friday as they cleared areas, sometimes pushing along people who had nothing to do with the protest. At one point, a group of tourists in town to watch an extreme fighting event found themselves moved from where they were standing in front of their hotel.

Another group of young men from Georgetown, Ont., saw the commotion from their hotel window and came out to see police tackle a man across the street and wrestle him to the ground.

"We've never experienced it," said a surprised Alec Littlejohn.

Jake Claer, his friend, said, "It's kind of absurd."

"Being from a small town, big city life's a little different," he said. "It's kind of cool."

Montreal police were aided by officers from the Quebec provincial police and nearby Laval. Observers were also on hand from police forces in Toronto, London and the Peel Regional Police Service to learn from the Montreal force's now-frequent experience in dealing with rowdy protests.

"They don't get the kind of protests we do here," one Montreal officer joked.

The march began a stone's throw from Montreal's main shopping district where uneasy merchants girded for the worst. There had been complaints from business owners in recent days, saying their profits plummet every time there's a demonstration because potential customers flee the commercial area.

Police advised people in the days leading up to the demonstration to stay out of the area.

Tempers flared as the march got underway, as they often have during the city's numerous recent protests. There were reports on social media of angry motorists inching their cars up against the street-clogging protesters.

Demonstrators blocked a couple of intersections by chanting and standing around with banners but were kept off main traffic arteries during the evening rush hour.

Last year, 200 people were arrested after the march, which co-incided with ongoing student protests in the province, turned violent.

Windows were smashed in the melee and police cars were vandalized.

Police this year were co-ordinating their response to the march with a high-tech command centre that links them with the fire department and the city's ambulance service.