"We have identified the disease as the dangerous bird flu which was found in Vietnam for the first time," Hoang Van Nam of the ministry-run veterinary department told Reuters.

Further tests would be done abroad to verify the type of bird flu and to determine if it is a threat to humans.

In 1997 and 1998, the H5N1 variant of avian influenza swept through Hong Kong's poultry farms, killing six people.

"The bird flu is a combination of sub-types under H and N and so far we have been able to identify only H5," Nam said. There are 15 sub-types under H and nine under the N categories.

Deputy Prime Minister Nguyen Tan Dung, in an official statement seen last week, ordered local governments to incinerate all chickens suspected of carrying the virus and said all farms where sick birds were found would be quarantined.

Chicken is widely consumed during Tet, the new year celebrations that lasts from January 21 to 27.

The deputy prime minister's comments were the first official acknowledgement of the disease, two weeks after veterinarians said around 500,000 chickens had been killed in two southern provinces of Long An and Tien Giang.

Bird flu has also spread to the country's financial capital, Ho Chi Minh City, where some consumers have already taken chicken off the menu.

"I love chicken but it's scary to eat the meat now. It kills chicken - who knows, it could kill us too," Nguyen Van Hue, a clothes shop owner, told Reuters, pointing at an empty chicken noodle shop on a busy street in commerce hub Ho Chi Minh City.

Chicken noodle soup is a popular breakfast dish in the southeast Asian country.

Vietnam does not export chickens. Dung has asked the agriculture ministry to seek foreign help to identify the sub-type of the virus and to find a cure.

Checkpoints have been set up to stop farmers dumping infected chickens at southern markets.

The country had 254 million livestock, including chickens, at the end of 2003.