Police say around 500 people have been arrested after an anti-G20 march in downtown Toronto ended in rioting.
Police cars were set on fire in at least two areas of the city.
Masked demonstrators broke off from the march and smashed store windows in a violent show of opposition to the summit.
Toronto’s police chief admitted his officers had struggled to contain the violence.
Thousands have been drafted in from across Canada, at a cost of more than a billion canadian dollars.