Small groups of protesters have clashed with police in Toronto as leaders from the world's richest nations and emerging economies gathered for the G20 summit.
Police cars were set on fire and storefronts were smashed on Saturday as at least 10,000 people marched to highlight issues like indigenous rights, poverty and climate change.
An emergency services spokeswoman told Reuters news agency that at least three people had been wounded in the protest.
Along with a heavy police presence, authorities shut down public transport and blocked streets leading into the centre of the city.
While most protesters remained peaceful, television images primarily focused on so-called "anarchists" who had aimed to face off with police along the three-metre high barrier that encircles the G20 meeting site.
Soon after the demonstrators arrived near the barrier, groups of black-clad protesters appeared to separate themselves from the larger group and confronted the hundreds of police shadowing the march.
Anti-G20 groups have been demonstrating in Toronto all week before the summit which follows a smaller meeting of Group of Eight (G8) industrial nations in the resort town of Huntsville in Ontario.
Security for the G8 and G20 summits has cost Canadian tax payers more than $1bn.
Avi Lewis, Al Jazeera's correspondent covering the protests, said many were angry at the money spent on the summit.
"One of the flash points has been the cost of the summit itself, it sparked a tremendous amount of outrage here in Canada, " he said.
"A recent poll showed that 78 per cent of Canadians thought the cost of the summit was unacceptable."
"In the last two G20 summits in Pittsburgh and London, the combined security cost was $25 million.
There is a feeling on the streets that this could be the most expensive and wasteful photo-op in the history of humanity," our correspondent said.
Liisa Schofield, a protest organiser, said that money spent on the summit should have been been used to provide shelter for homeless people.
"There is 10,000 people who live on the streets of Toronto and there are 70,000 people on the waiting list for social housing."
The money the Canadian government has decided to spend on this summit "could have paid for all 80,000 people who are currently without proper housing to live in a proper apartment for a year," she said.