South Korea´s agriculture ministry said on Monday it had found a third case of highly pathogenic bird flu in North Cholla province south of Seoul.

Last month South Korea confirmed its first two outbreaks of the H5N1 strain in about three years, saying the virus had been found at two poultry farms close to each other in North Cholla province.

The third case was discovered at a quail farm in the same province about 170 km (100 miles) south from Seoul, some 18 km from the original outbreak, according to the ministry.

"The case has been confirmed as the H5N1 strain of avian influenza," the ministry said in a statement, adding thousands of birds at the farm had died over the past four days.

The fresh case emerged after South Korea had completed culling all 760,000 poultry near the two farms already discovered to have been infected with H5N1.

Between December 2003 and March 2004, about 400,000 poultry at South Korean farms were infected by bird flu.

During that outbreak, the country destroyed 5.3 million birds and subsequent testing in the United States indicated at least nine South Korean workers involved in the culling had been infected with the H5N1 virus, but none developed major illnesses.