The H5N1 bird flu virus has been found on a poultry farm in Laos, the U.N. Food and Agriculture Organization (FAO) said on Friday.

The outbreak occurred on a commercial farm 25 km (15 miles) south of the capital Vientiane where about 2,500 chickens died last week, according to state media reports.

The same farm experienced an outbreak in early 2004 when the virus swept through parts of Asia. Since then, the only previous discovery of the H5N1 virus in Laos had been in a single duck in May this year.

"The government of Laos has taken immediate action to control the spread of the virus by culling all chickens in the farm, disinfecting the farm and imposed movement restrictions within the five kilometer surveillance zone," said Wantanee Kalpravidh, FAO regional coordinator for Avian Influenza Projects.

Further investigation was needed to determine the source of the outbreak, she said in a statement.