Greenpeace in April announced it had found genetically engineered rice at markets in central Hubei province.

"We are sure that people are consuming it unknowingly," Greenpeace campaigner Sze Pang Cheung said at a news conference in Beijing, referring to rice that had been modified to contain the bacteria Bacillus thuringiensis (Bt), which produces a toxin that kills pest.

"We are now facing the contamination of the most important staple crop in the whole world," Sze said.

Pressure to launch GMO rice in China comes at a time when the country is facing a tough task in raising urban grain output and narrowing the income gap between farmers and urban citizens.

Proponents of genetically modified crops say they will improve yield and reduce plants' vulnerability to pests. Opponents say pests will develop greater resistance to the modified crops, and that the techniques undermine biodiversity and could prove dangerous for human consumption.

GMO APPROVAL

China, the world's largest producer and consumer of rice, is testing several strains of genetically modified rice and is expected to grant approval for the commercialisation of such rice as early as this year.

China, one of the world's largest importers of GMO crops, said last month it had ratified a UN treaty that aims for more transparency and control over trade in genetically modified foods.

"China is sending a strong message to the world that it is no dumping ground for GM crops," Sze said at the time.

Chinese genetically engineered rice may have already made its way into exports of rice or rice-based products, Sze said on Monday.

But he acknowledged Greenpeace had no direct evidence of Bt rice leaving China.

Greenpeace estimated that up to 29 tonnes of genetically modified Bt rice seeds, capable of producing as much as 14,500 tonnes of rice, were illegally sold in Hubei this year.

"We think it is unacceptable and irresponsible that they are not taking this issue seriously because rice is the most important staple in China," Sze said.