Toronto: Police raided a university building and rounded up hundreds of protesters on Sunday in an effort to quell further violence near the G20 global economic summit site a day after black-clad youths rampaged through the city, smashing windows and torching police cars.
The violence shocked Canada, where civil unrest is almost unknown. Toronto police on Sunday said they had never before used tear gas until Saturday`s clashes with anti-Globalisation activists.
Police said they have arrested more than 600 demonstrators, many of whom were hauled away in plastic handcuffs and taken to a temporary holding centre constructed for the summit.
Police adopted a more aggressive strategy on 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.
No serious injuries were reported among police, protesters or bystanders, Toronto Police Constable Tony Vella said on Sunday.
Thousands of police officers in riot gear formed cordons to prevent radical anti-globalisation demonstrations from breaching the steel and concrete security fence surrounding the Group of 20 summit site.
Security was being provided by an estimated 19,000 law enforcement officers drawn from across Canada. Security costs for the G20 in Toronto and the Group of Eight summit that ended on Saturday in Huntsville, 140 miles (225 kilometres) away, were estimated at more than USD 900 million.
Prime Minister Stephen Harper deplored the actions of a "few thugs" and suggested the violence justified the controversial cost. "I think it goes a long way to explaining why we have the kind of security costs around these summits that we do”, he said.
The disorder and vandalism occurred just blocks from where US President Barack Obama and other world leaders were meeting and staying.
On Sunday, protesters gathered at a park near the detention centre — about 2 1/2 miles (four kilometres) east of where the leaders were meeting.
Plainclothes police jumped out of an unmarked van, grabbed a protester off the street and whisked him away in the vehicle. The protest was then quickly broken up by riot police, who set off a device that created a cloud of smoke that sent protesters running down the street. Vella said it was not tear gas.