The European Commission urged member states this week to intensify controls on genetically modified foods out of fear they might contain an illegal GM product that Greenpeace and Friends of the Earth said came from China.

"We have not approved a single case of the commercial production of GM rice," foreign ministry spokesman Qin Gang told a regular press briefing.

"We follow the principle of scientific experiment and supervision according to law," he said.

The pressure groups tested samples of rice products such as vermicelli, rice sticks and other processed foods in Britain, France and Germany.

Five positive samples were found containing an illegal GM product, traced to China and not approved anywhere in the world, they said.

The European Commission has asked EU states to provide test results by Thursday and said it would write to Chinese authorities seeking further information.