By Cameron French and Pav Jordan
TORONTO (Reuters) - Police in Toronto fired tear gas on protesters for a second straight day on Sunday as new violence surrounding the G20 summit erupted and the arrest tally climbed towards 600.
The latest clashes occurred as several hundred protesters marched on a temporary detention centre for demonstrators arrested in riots on Saturday during which police used tear gas against the public for the first time ever in Canada's most populous city.
A police spokeswoman confirmed that officers on Sunday fired what are known as muzzle blasts, or "individual applications of tear gas" that are used typically against individuals at close range.
A Reuters witness in front of a former film studio in Toronto's port area where police are detaining protesters said he heard a loud "thunk" and saw clouds of smoke billow before police charged, scattering the crowd.
The weekend violence started on Saturday afternoon after groups of masked anarchists broke away from a larger, peaceful demonstration against the Group of 20 summit of rich and emerging economies, which ends on Sunday.
Protesters, many dressed in black gear, smashed windows of downtown stores and banks and torched police cars in a protest that police finally brought under control with tear gas and mass arrests.
"What we're prepared for today is more of what we saw yesterday," a police spokesman said. "We'd like to see demonstrations remain peaceful."
Protesters said police were being heavy-handed, using tactics that instigate violence rather than quell it. They also criticized the media for focussing coverage on violent clashes rather than the broader peaceful marches.
"This is the criminalization of dissent," said Chelsea Flook, with the Toronto Community Mobilization Network, just after police raided a protester convergence place run by the group in search of members of the Black Bloc, which police say instigated the riots over the weekend.
Black Bloc are anarchists who wear black clothing and ski masks to avoid being identified as they attack police and public property. They meld into over-all protest groups and often work to create riot situations.
BRICKS, ROCKS AND STICKS
After a day when police admitted losing control of a violent and fast-moving crowd, the arrests came fast on Sunday.
Among those detained, for charges ranging from mischief to assaulting police, were four people who climbed through the sewer system and emerged near the lock-down area where world leaders were attending the summit. Police said they were urgently sealing sewer access near the zone.
About 70 people also were detained after police raided the University of Toronto's downtown campus. Police said they seized weapons, including bricks, rocks and sticks.
It was not clear if they were connected to an anarchist group that has announced a "Demonstration Against Prison" at 5 pm (10 p.m. BST), just as G20 leaders wrap-up the two days of meetings in Toronto.
By mid-afternoon, the city had taken on a state of relative calm, with smaller, orderly, peaceful demonstrations around the financial core by groups clamouring for G20 leaders to try harder to find ways to fight poverty and the effects of climate change.
Thousands of cyclists made their way lazily around the Ontario legislative buildings at Queens Park, where a day before police and protesters had their biggest clashes.
Anti-G20 groups started demonstrating in Toronto before the summit, which followed a smaller meeting of Group of Eight industrial nations in a resort town north of Toronto. The security bill is set to come in at about $1 billion (644 million pounds).
Such international meetings have been the target of protest groups for years, including demonstrations that disrupted trade talks in Seattle in 1999.
(Additional reporting by David Ljunggren, Claire Sibonney and Janet Guttsman; Editing by Mario Di Simine)
