The accession of Cambodia and Nepal to the World Trade Organisation is likely to provide a momentary and welcome flush of success to the five-day conference, which is beset by deep divisions in key areas.

Ministers meeting here from the 146-strong trade body are scheduled to rubberstamp the entry of the two nations, making them the first least-developed countries to complete the WTO's accession process.

Despite tight security, the talks, which got underway in this Mexican seaside resort on Wednesday, were overshadowed on their opening day by violent scenes in downtown Cancun.

A South Korean man, the head of the country's Federation of Farmers and Fishermen, died after stabbing himself in protest against WTO rules on agriculture.

"We all regret this sad incident," WTO director-general Supachai Panitchpakdi said after the death of 55-year-old Lee Kyang Hae.

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

A mass security operation kept up to 5,000 demonstrators more than 10 kilometres (six miles) away from the site of the talks but could not prevent several hundred protestors clashing with police.