As the clashes between the protestors and the police took place all day and into Tuesday night, the Seattle city mayor declared an emergency and imposed a curfew.

The conference finally got under way five hours late after the police cleared the protestors out of the city center. The Paramount Theatre and the Seattle conference centre where the meetings were being held was surrounded by phalanxes of armed police wearing gas masks.

Commerce and industry minister Murasoli Maran who spoke on the truncated opening day of the conference firmly opposed any moves to bring in labour standards and environment as the core issues in the World Trade Organisation.

"Any further move will cause deep divisions and distrust that can only harm the formation of a consensus on our future work programme," Maran said even as about 16,000 labour union members and other workers staged a march to voice their demand that worker rights be a part of future trade deals. The protestors said the free trade ideals espoused by the WTO benefit big business at the cost of workers, the environment and communities.

This is the first time in WTO history that a global conference of 134 member countries has been blocked, albeit temporarily, by demonstrators.

President Bill Clinton, an advocate of free trade, nevertheless sympathised with the protestors and said that trade agreements should take into consideration labour and environmental concerns.

In scenes reminiscent of US civil rights and anti-war protests of the 1960s, police in riot gear sprayed tear gas and shot rubber pellets they called "stingers" to clear protestors who had clogged the streets and blocked access to the meeting venues.

The streets were littered with glass and other debris after activists smashed store front windows, sprayed graffiti and set trash containers alight to vent their anger at the WTO.

Seattle police admit they were taken by surprise. "These demonstrators, particularly those who were bent on violence and destruction, made it difficult for us," Police chief Norm Stamper conceded. "It was a calculated strategy of major, active and threatening disturbances."

At the posh Westin Hotel, where US trade representative Charlene Barshefsky and her Japanese counterparts were staying, guests were told to go to their rooms for fear demonstrators would storm the building.

Barshefsky said negotiators had already made progress toward narrowing their differences over agriculture and electronic commerce. "We're very much on track," she said. But other diplomats were sceptical a breakthrough was at hand. The US is seeking to create a panel within the WTO to address labour issues.