Lee Kyang Hae, 55, who headed South Korea's Federation of Farmers and Fishermen, stabbed himself in protest against the WTO, "which destroys Korea's economy and its agriculture," a fellow farmer said.

Lee climbed onto a high security fence during a violent protest and waved a banner that read "WTO Kills Farmers." He then stabbed himself in the chest and later died in hospital.

"His death is not a personal accident but reflects the desperate fighting of 3.5 million Korean farmers," said Song Nan Sou, president of the Farmers Management Association, one of several South Korean groups taking part in demonstrations at this upmarket Mexican seaside resort.

"We all regret this sad incident," World Trade Organisation Director-General Supachai Panitchapkdi said.

"This self-inflicted wound has resulted in his death, so we do regret it," he said.

About 5,000 activists joined the protest and about two dozen broke through eight-foot-high metal barriers to attack police on the edge of Cancun's upscale hotel zone.

"We are going in. We are going in," a South African trade unionist screamed through a loudspeaker urging protesters to storm a long strip of beach hotels and fast food restaurants.

Demonstrators threw chunks of paving stones, sticks, metal bars and bottles at police, who fought back with batons and tear gas. More than a dozen people were inured as police held off the protesters.

Violent protests have become a staple of international trade and finance meetings since rioting at a WTO meeting in Seattle in 1999. Italian police shot dead a protester at a summit of industrialised nations in Genoa in 2001.

The 146-nation WTO opened its five-day meeting in Cancun with serious divisions on a host of disputes, topped by agricultural subsidies in the United States and Europe.

British development charity Oxfam yesterday called on political leaders at the WTO talks to commit themselves to changing Europe's agricultural subsidy regime, which it said was biased toward helping the bloc's richest producers most.

Oxfam said Europe's Common Agricultural Policy (CAP) was also preventing poorer nations, which receive much of the cheap, heavily subsidised food, from pulling themselves out of poverty.