MONTREAL -- Anti-capitalist demonstrators smashed windows at a downtown Montreal police station on Sunday as protesters held their annual May Day march.

The incidents occurred about one hour into the demonstration and prompted police to fire off canisters of tear gas and warn protesters to disperse.

Police reported about 10 arrests and one minor injury.

Earlier in the day, a union-organized protest was held without a hitch.

More than 80 people were arrested in the anti-capitalist protest last May 1.