South Korea's Agriculture Ministry has confirmed the country's sixth outbreak of bird flu among poultry, despite government efforts to contain the virus.

Officials said Saturday that the latest case was found at a farm in Ansong, about 70 kilometers south of Seoul. The outbreak was caused by the H5 virus, but further tests are needed to determine whether it is the H5N1 strain that can be deadly to humans.

Quarantine authorities plan to cull poultry within three kilometers of the infected farm.

More than two million birds have been culled since November, when South Korea announced its first bird flu outbreak in about three years.

More than 160 people have died from bird flu since the outbreak began in late 2003, mainly in Asia.

Most human cases have resulted from contact with sick birds. But health authorities fear that the virus could mutate into a form easily transmissible by human-to-human contact.