Indonesia, which said Wednesday that it had discovered new cases of the disease, said it would take around three years to eradicate it.

Fifteen of Thailand's 76 provinces have been hit, including northeastern Nong Khai that borders Laos - one of many Asian countries hit earlier this year by the disease that killed 16 people in Vietnam and eight Thais.

"Bird flu is confirmed in three districts of Bangkok. They are Don Muang, Nong Chok and Min Buri," Yukol said, referring to areas on the outskirts of the capital.

Thailand, the world's fourth-biggest chicken exporter in 2003, has culled 160,000 fowl since the new outbreak was confirmed on July 3, officials said.

There have been no reports of anyone falling ill from bird flu in the latest outbreaks, but the government has put Thailand on high alert, ordering officials to rush anyone to hospital who shows symptoms resembling those of bird flu.

In Indonesia, the government is taking strict measures to fully stamp out the disease, but it will take time, Agriculture Minister Bungaran Saragih told reporters.

"Culling and vaccinations cannot immediately clear the outbreak, thus we need around three years to be fully certain that we are free from the disease," Saragih said.

Most of the previously affected areas were under control, he said.

The disease has appeared again on farms on Java, Indonesia's most populous island. It killed nearly 2,000 chickens in East Java from June to early July, and more than 3,000 in West Java in May.

The government has acted to prevent the disease from spreading to new areas through massive nation-wide vaccinations, bio-security regulation and culling.

Authorities say no case of human infection have been found in Indonesia so far.