Protesters hurled tear gas, asphalt and other debris and police in riot gear and on horseback made dozens of arrests Monday outside a hotel where finance ministers from major industrialized nations and developing countries were set to meet.
Three policemen were slightly injured and 39 protesters were in custody after the clash.
Police spokesman Andre Durocher said the detained protesters would face charges ranging from unlawful assembly and participating in a riot to assaulting a police officer. He said some were to be released later Monday night while others likely would remain in custody.
Some protesters carried signs that read "Resist" and "Eat the Rich," while others wore masks and brandished clubs. They began fighting back when police tried to prevent them from going into surrounding streets: Some hurled tear gas, chunks of asphalt, paint balls and bottles at police armed with shields, batons and pepper spray.
Dozens of officers eventually cleared the area of demonstrators and remained on guard outside the Sheraton Hotel in downtown Montreal, where the two-day meeting of the G-20 finance ministers is scheduled to begin Tuesday afternoon.
While protesters accused police of overreacting, Durocher said some demonstrators came looking for trouble.
"They were throwing pieces of asphalt, they were throwing bottles," he said. "I don't call that a peaceful protest. I have serious doubts about people's motivation."
Created a year ago, the G-20 is intended to facilitate discussions between the world's wealthiest industrialized countries and some of the biggest developing nations, including India and Brazil.
Protests by a broad coalition of groups concerned about the environment, poverty, workers' rights and other issues have become commonplace at international meetings involving global trade.
Street violence disrupted a World Trade Organization meeting in Seattle last December, and clashes also have occurred at gatherings this year, including an International Monetary Fund meeting in Washington and an Organization of American States meeting in Ontario.
