Police used teargas and batons to disperse demonstrators who hurled rocks and bottles, according to AFP reporters. One man of Asian origin and a Mexican woman were injured.
Hundreds of demonstrators, many masked, took part in the clashes, which followed a protest by about 5,000 people.
Barriers and a massive security force deployment kept demonstrators more than 10 kilometres away from the Cancun convention center where ministers from the 146 member WTO were seeking to relaunch a free trade agenda.
About 30 inside the conference hall jeered WTO director general Supachai Panitchpakdi during his opening address.
“We will only achieve the objectives of trade and development if there are benefits for all,” Supachai told the meeting.
As he spoke, the activists, some chanting, some with mouths taped, held up pieces of paper denouncing the WTO as “anti-development” and undemocratic.
They then shouted “shame” and were escorted out of the room where 2,650 delegates, journalists and non-governmental organization (NGOs) representatives had gathered.
Supachai told delegates: “The eyes of the world are on this conference and people will judge us by the choices we make.
“We face a choice here in Cancun: either we continue to strengthen the multilateral trading system and the world economy or we flounder and add to the prevailing uncertainties.
“We have to deliver on the first choice ... anything else will delay the chances of our peoples to change their lives for the better. This would be unacceptable to us and most importantly to them.”
The gathering has also sparked protests from Asia to Europe.
But the damage done to the WTO by the delegates themselves could prove to be far greater than that caused by activists, notably if some delegations carry out a threat to walk away from the talks if their demands for farm trade reforms are ignored.
Agriculture is the most contentious issue thwarting efforts by the WTO to implement the Doha Development Agenda, an ambitious road map for eliminating global trade barriers adopted in the Qatari capital, Doha, in November 2001.
The issue has split the WTO into several camps. Developing countries, the United States and the Cairns group headed by Australia all want a quicker and more comprehensive abolition of trade-distorting export subsidies to farmers than the European Union and Japan.
UN Secretary General Kofi Annan, in a speech read to the opening session, drew applause when he urged delegates to scrap subsidies and abolish trade practices that keep the developing world mired in poverty.
“Instead of open markets, there are too many barriers that stunt, stifle and starve,” Annan said. “Instead of fair competition, there are subsidies by rich countries that tilt the playing field against the poor.”
On Wednesday evening, delegates were to discuss a proposal by four African states that calls for the elimination of cotton production and export subsidies over a period of four years.
African cotton growers say agricultural subsidies in the United States threaten the survival of the sector in impoverished African countries.
But US cotton growers have vowed to launch a concerted effort to thwart any attempt to trim their subsidies, which come to roughly 3.9 billion dollars annually.—AFP