Avian flu has claimed two more lives in Asia -- one in Thailand and the other in Vietnam -- bringing the toll so far to 12.

Thai Health Minister Sudarat Keyuraphun announced the death of a 58-year-old-woman in the Suphanburi province. Autopsy of the woman, who died last week, showed the cause of death was the chicken flu virus.

An official said five others were suspected to have been infected with the virus, one of whom has died. However lab results to confirm the cause of death takes a week.

The official said the man, who was involved in culling of chickens, had reportedly died of the virus after he apparently took off his gloves to smoke a cigarette. Last week two children died in Thailand due to bird flu and another is in hospital battling the disease.

Avian flu has galloped across poultry farms in Asia affecting ten countries. In Vietnam and Thailand, the disease has jumped to humans.

There are now 18 suspected human cases in Thailand, 10 of whom have died.

According to the Thai News Agency, at least 25.9 million chickens have been slaughtered to stop the spread of the disease. Sixteen provinces are still affected by the flu.

Thailand's poultry industry - the world's fourth largest - has suffered from bird flu outbreak. The European Union, Japan and other major markets have banned Thai chicken products.

Meanwhile, the World Health Organisation is probing the deaths of two Vietnamese sisters who might have caught the disease through contact with their brother. If proved, it could be the first human-to-human transmission of bird flu.

There is, however no evidence yet of a new strain that can easily be passed among people.

"The situation is always going to have a question mark hanging over it," WHO spokesman Bob Dietz said in Hanoi.

The Food and Agriculture Organisation has appealed for international aid for Asian farmers, saying they may otherwise stop killing the poultry flock. Killing the infected chickens is vital to prevent the spread of the disease.

The disease has hit Cambodia, Indonesia, Japan, China, Laos, Pakistan, South Korea and Taiwan, other than Thailand
and Vietnam.