Montreal police will be on high alert today for the city's Formula One Grand Prix race after a chaotic protest last night.
An anti-capitalist group is calling for disruptions on the subway line used to get to the track.
The Formula One race gets underway this afternoon at Circuit Gilles-Villeneuve, on an island just outside the city.
There has been a heightened police presence during the Grand Prix festivities in downtown Montreal and at the race track itself.
The event has become the target of demonstrations against student tuition fee increases and capitalism in general.
Last night's demonstration ended in clashes between protesters and riot police and least four police cruisers were vandalized.
In total 28 people were arrested, including a taxi driver who could face charges for fleeing the scene. Police say he got out of his cab to argue with a crowd of protesters and it rolled down a hill, injuring three people.
Today's protest is organized by an anti-capitalist group that has often been involved in skirmishes with police. The idea appears to be to pack the subway with as many as possible, making it difficult for fans to get to the race.
"We're all going to the Grand Prix ... AT THE SAME TIME!" reads a posting on the group's website.
"Just to see how many people can enter the subway? Upon arriving on the island you can turn around and start again. Just for fun."
The subway protest is also being promoted on a popular student website.
"Don't get aboard the trains until you receive the signal," the post says.