Up to 30 more tigers are reported to be ill at the The Sriracha Tiger Zoo in central Chonburi province, home to more than 200 Bengal tigers.

"All 23 dead tigers had bird flu. We believe that the tigers contracted bird flu because they ate chicken carcasses, and we believe the carcasses had bird flu," the BBC quoted Charal Trinvuthipong of the Bird Flu Prevention and Elimination Center as saying.

'The latest outbreak of bird flu has ravaged Asian poultry, and left more than 30 people dead. It has also affected domestic cats in Thailand, although health officials have played down the risk of the animals passing the disease to humans,' the BBC said.

Health experts fear that the virus might combine with a regular human influenza strain and create a deadly mutant which could trigger a human flu pandemic.

Describing tackling the disease as the country's top priority, Prime Minister Thaksin Shinawatra had earlier set an October 31 deadline to eradicate bird flu from Thailand.

Complete coverage: Bird Flu