South Korean quarantine officials are to slaughter 236,000 poultry after an outbreak of the H5N1 form of bird flu at a chicken farm.
The H5N1 virus began hitting Asian poultry stocks in 2003
The outbreak occurred at a farm in Iksan, about 250km (155 miles) south of Seoul, earlier this week.
Test results confirmed the outbreak was caused by a type of H5N1 virus, the country's agriculture ministry said.
It said all birds within a 500-metre (1,650-foot) radius would be culled to prevent the virus from spreading.
The ministry also said it would limit the movement of about five million chickens and ducks from 221 farms within a 10-kilometre (six-mile) radius of the outbreak.
Park Yong-jong, a city official in Iksan, said the cull would begin on Sunday morning.
Lee Sang-gil, head of the agriculture ministry's livestock bureau, said no people had been infected.
South Korea killed 5.3 million birds during the last known outbreak of bird flu in 2003.
The H5N1 virus began hitting Asian poultry stocks in 2003, and has killed at least 153 people worldwide.
Most human cases have resulted from contact with infected birds.
Scientists fear the virus could mutate into a form that is more easily transmitted between people, possibly creating a pandemic.