The new outbreak is in Jingshan county in Hubei province, which borders the Anhui and Hunan provinces. These provinces were hit by the H5N1 virus last month.

Although there have been no confirmed human infections with the disease in China, the country's Prime Minister Wen Jiabao warned last week that the country was facing a "very serious situation".

The disease has already killed more than 60 people in Asia and with increasing infection of birds, it is only a matter of time before human cases emerge, say experts.

Western media reports say that up to four human cases of the virus are being investigated in China.

And according to the BBC, the authorities have warned that fake bird vaccines have been sold in Liaoning province in the north-east, which has seen four outbreaks of the disease already. This could mean that millions of birds have not been properly inoculated and have the disease but are showing no symptoms.

Around 2.5 million poultry have been culled in this area, and a further 30,000 will be killed in Hubei.