Police with shields and clubs pushed back the rogue protesters who tried to head south toward the security fence surrounding the perimeter of the Group of 20 summit site. Some demonstrators hurled bottles at police.
"We have never seen that level of wanton criminality and vandalism and destruction on our streets," Toronto police chief Bill Blair said.
The roving band of protesters in black balaclavas shattered shop windows for blocks, including at police headquarters, then shed some of their black clothes, revealing other garments, and continued to rampage through downtown Toronto.
Protesters torched at least three police cruisers in different parts of the city, including one in the heart of the city's financial district. One protester jumped on the roof of one before dropping a Molotov cocktail into the smashed windshield.
Blair said the goal of the militant protesters was to draw police away from the security perimeter of the summit so that fellow protesters could attempt to disrupt the meeting.
Police arrested 130 people Saturday, but Blair said many suspects remain at large.
Blair said officers have been struck by rocks and bottles and have been assaulted, but none was injured badly enough to stop working.
A stream of police cars headed to Toronto to reinforce security there after the smaller Group of Eight summit ended in Huntsville, Ontario, about 140 miles (225 kilometers) away. Security was being provided by an estimated 19,000 law enforcement officers drawn from all regions of Canada, and security costs are estimated at more than US$900 million.
The vandalism occurred just blocks from where President Barack Obama and other world leaders were meeting and staying.
"These images are truly shocking to Canadians," Canadian Public Safety Minister Vic Toews said in a statement. "We are taking all measures necessary to ensure Canadians, delegates, media and international visitors remain safe."
Previous major world summits also have attracted massive, raucous and sometimes destructive protests by anti-globalization forces.
Police in riot gear and riding bikes formed a blockade, keeping protesters from approaching the security fence a few blocks south of the march route. Police closed a stretch of Toronto's subway system along the protest route and the largest shopping mall downtown closed after the protest took a turn for the worse.
"Free speech is a principle of our democracy. But the thugs that prompted violence earlier today represent in no way shape or form the Canadian way of life," said Dimitri Soudas, the chief spokesman for Canadian Prime Minister Stephen Harper.
A media bus taking photographers and cameramen to a hotel where the G-20 leaders will have dinner was turned back after police deemed it unsafe.
Dozens of police officers later boxed in a number of protesters from both sides of a street in a shopping district. The protesters encouraged the media to film it and they sang 'O Canada', Canada's national anthem, before being allowed to disperse.
At another location at the provincial legislature police also boxed in demonstrators before tackling some and making arrests.
Saturday's protest march, sponsored by labor unions and dubbed family friendly, was the largest demonstration planned during the weekend summits. Its organizers had hoped to draw a crowd of 10,000, but only about half that number turned out on what was a rainy day.
Toronto's downtown resembles a fortress, with a big steel and concrete fence protecting the summit site.
On Friday, hundreds of protesters moved through Toronto's streets, but police in riot gear intercepted them, preventing them from getting near the summit security zone downtown.
Previous global summit protests have turned violent. In 1999, 50,000 protesters shut down World Trade Organization sessions in Seattle as police fired tear gas and rubber bullets. There were some 600 arrests and $3 million in property damage. One man died after clashes with police at a G-20 meeting held in London in April 2009.
At the September G-20 summit in Pittsburgh, police fired canisters of pepper spray and smoke and rubber bullets at marchers.
This program aired on June 27, 2010. The audio for this program is not available.