Police in Montreal arrested dozens of protesters ahead of Sunday's Grand Prix, as Canadian students rallying for months over tuition hikes used the Formula One event to highlight their cause.

Police spokeswoman Annie Lemieux said about 30 arrests made on Sunday were pre-emptive in nature, but six people were charged with criminal offenses including "intimidation and threats made to police."

Shield-wielding riot police had pushed back and chased hundreds of protesters amassed in the downtown shopping district late Saturday, making 28 arrests and pushing several demonstrators, some in masks, to the ground.

Protesters -- mixed in with thousands of race fans and passers-by -- booed and cursed before confronting police, who shouted and unleashed pepper spray. Sirens blared and people occasionally screamed from the panic of being crushed.

For four months, students, joined by anti-capitalists, have held protests against plans by the Quebec provincial government to increase tuition fees by 75 percent.

"We are in a real social crisis in Quebec. And at the moment we are witnessing police brutality, for no purpose, really," University of Montreal student Zac Daoust Lefebvre told AFP.

Negotiations between student groups and the province have broken down, and the protest movement have since morphed into a larger campaign of perceived government corruption, mismanagement and injustice.

Student groups are eager to take advantage of the expanded media presence and international visitors in Montreal for Sunday's Grand Prix -- won by Britain's Lewis Hamilton -- to publicize their tuition fight.

Police have responded with a bigger footprint, deploying numerous officers in the metro system and around the Circuit Gilles-Villeneuve to search bags and check identification documents.

"We're not conducting a systematic search," said another police spokesman, Mark David. "We only ask to search a bag if we believe it may contain blunt weapons."

Shortly before 8:00 am (1200 GMT), a bomb alert in the metro system nearby briefly interrupted traffic before it turned out to be false. A man in his 50s was arrested in connection with the incident.

A significant police presence also kept guard at the Jacques Cartier Bridge leading to the race track.

Several dozen police officers, including mounted patrols, kept watch as fans made their way onto Saint Helen's Island, next to Ile Notre-Dame where the track is located, ahead of the start of the race at 2:00 pm (1800 GMT).

On Saturday night, 22-year-old Jay Ilan, a recent Concordia University graduate, said police should do their job but that the "brutality could be avoided."

"They're dragging people across the ground. And they're trying to cover it up. They're trying to cover each other. It shows that they know what they're doing is wrong," he said, shaking his head.

Only a few meters (yards) away from the unrest, hundreds of well-heeled partygoers danced and drank into the night on terraces and in bars on Crescent Street to celebrate the Grand Prix.

Some held plastic cups of beer and shook their heads, shouting "get a job" to the protesters.

AFP Photo/Michel Viatteau