Police Constable Rob McDonald said several dozen people were taken into custody at a University of Toronto building for allegedly wielding "street-type weaponry" that included bricks, bats, sharpened sticks and bottles of fluid -- "items you don't need for a weekend in Toronto," The Globe and Mail reported. No guns or knives were found, he said.
Canadian TV network CTV reported police fired rubber pellets and blank rifle shots to push back about 100 demonstrators during what apparently had been a peaceful sit-in outside a detention center.
The network said the group was chanting "peaceful protest, peaceful protest" when police moved into the crowd to grab a known anarchist. That triggered a reaction from the group, prompting the police response and more arrests.
On Saturday, an apparent breakaway group of about 70 protesters set fire to police cars, hurled bricks, and smashed store and office windows, the Toronto Star reported.
The protests, which drew thousands of demonstrators to the economic summit, halted downtown subway service much of Saturday and forced the closing of some hospitals and businesses as police corralled demonstrators by the busloads.
Officers, some pelted with bricks or other projectiles, fired tear gas for the first time in Toronto's history at Queen and Peter streets, Toronto Police Chief Bill Blair said. "We have never seen that level of wanton criminality and destruction on our streets," Blair said.
Some protest organizers told the newspaper police had intimidated and arrested peaceful demonstrators.
The Guardian confirmed Jesse Rosenfeld, a Canadian journalist freelancing for the British newspaper, was arrested during the protests Saturday night.
Steve Paikin, host of public station TVOntario's "The Agenda," witnessed the arrest and tweeted that he saw Rosenfeld, 26, being held by two officers while another punched him and drove an elbow into the man's back. Paikin called it "totally unnecessary" use of force and "police brutality."