China said on Wednesday it had confirmed an outbreak of H5N1 bird flu among wild birds in remote far-western Qinghai province and in Tibet.

About 400 wild birds had been found dead "recently", Xinhua news agency said, quoting the Agriculture Ministry.

An outbreak of the H5N1 strain at Qinghai Lake last May killed thousands of birds and that particular strain has since been found in Europe, Africa and the Middle East.

"It is not unusual as it happened last year, but you need to be very careful to make sure people do not get infected," Roy Wadia, spokesman for the World Health Organisation in China, told Reuters by telephone.

The governments of Qinghai and Tibet had disinfected the region where the birds were found, Xinhua said, adding no domestic poultry had been affected.

China has reported at least 18 human infections of the H5N1 strain, 12 of which have been fatal. It has reported almost 40 outbreaks of bird flu in poultry across a dozen provinces over the past year.

Epidemiologists fear that bird flu could mutate into a form where it could pass easily among humans, potentially triggering a pandemic in which millions could die.

State media said two weeks ago China had tightened controls in Yushu county, about 800 km (500 miles) from the Qinghai capital Xining, where an outbreak of the H5N1 strain among wild birds was reported at the beginning of the month. At least 123 wild birds had been found dead.

Health experts see the country as being particularly at risk because of its huge human population and many poor, remote areas.