TORONTO [06.26.10] – Masked protesters rioted across downtown Toronto on Saturday, setting police cars ablaze and smashing store windows in a violent show of opposition to the G20 summit.

Toronto police chief Bill Blair admitted police had struggled to control the crowds, and had used tear gas on one occasion, after warning people to stay away from trouble spots. "We have never seen that level of wanton criminality and vandalism and destruction on our streets," he told an evening news conference.

Police said they have arrested more than 600 demonstrators, many of whom were hauled away in plastic handcuffs and taken to a temporary holding center constructed for the summit.

Police adopted a more aggressive strategy Sunday by going into the crowd to make arrests, compared to the previous day when they stood back as protesters torched four police cars and broke store windows.

Bridie Wyrock, 20, from Cleveland, Ohio, said she was arrested for public mischief for sitting on a street in the financial district. Wyrock, held for 19 hours before being released, said there weren't enough toilets and said some people resisted detention, but said police treated most people with respect.

"They put us in cages, blocked off on all three sides," Wyrock said. "It was cold and dirty."

An anti-poverty group called The Global Call to Action Against Poverty criticized the protesters who committed violence.

"A bunch of pimply faced teenagers trashing shops and burning cars does not help anyone," said Rajesh Latchman of GCAP South Africa. "These hooligans obscure the real issues."