Police slapped $638 fines on 132 demonstrators and arrested five others on criminal charges at an anti-capitalist demonstration Thursday.

A large group of Montreal police riot squad officers encircled the demonstrators at the 6 p.m. march and corraled the participants soon after they convened near Papineau and Ontario.

Police had deemed the CLAC demonstration illegal, as organizers failed to provide an itinerary for their march, as required under municipal bylaw P6.

Other smaller groups of marchers involved in the same CLAC rally were also later encircled, including one at St. Catherine near Plessis and another near Place des Arts.

A police representative later reported that criminal charges will be laid against five particpants for such offences as mischief and armed assault.

At one point police, who appeared to greatly outnumber the demonstrators, tweeted that several projectiles had been tossed their way. One demonstrator was seen being loaded into an ambulance with a cut over the eye, while another received medical attention after complaining of heart palpitations. In all, four were treated for minor injuries.

Participants headed to the Rosemont metro where they planned to demonstrate but a critical mass failed to materialize, leaving dozens of officers standing by at the ready and the protest appeared to end soon after.

The CLAC group was apparently prepared to counter certain police tactics, for example they had a siren at the ready to warn of police encirclement movements, however it never sounded as the marchers were stopped swiftly, after walking about 100 metres from their meeting point before being kettled.

Police duplicated the smothering strategy they employed to counter an anti-police brutality rally on March 15.

"What the P6 bylaw is doing, in practice, is putting an end to the right of protest," said CLAC representative Catherine Tremblay. "So yes, we are trying to deploy strategies to allow people to express their political opinions in the streets."

Montreal police representative Ian Lafreniere said that they were ready to react to the demonstrators' approach.

"It's not the first time that demonstrators take that approach. They use social media to set meeting points and form small groups, so as a result we made arrests in five groups rather than in one," said Lafreniere.

Other rally peaceful

Another separate rally was held outside of the premier's Montreal office at McGill College near Sherbrooke. It was organized by union officials and was not deemed illegal, as organizers had provided their route in advance.

That demonstration proceeded from McGill College south on Peel without incident.

Last year police arrested 450 at demonstrations in Montreal on May 1, long known as International Workers Day.

Some observers attributed the lower number of participants partially to the opening of the second-round hockey playoff series between Montreal and Boston, which kicked off at around the same time.

Other protests were slated to be held in a variety of other cities, including Quebec City, Longueuil, Sherbrooke and Gatineau.

-With a file from The Canadian Press