South Korea has killed 4.85 million birds since the deadly H5N1 strain of bird flu broke out earlier this month for the first time in more than a year, said Agriculture Ministry official Jin Pil-sik on Monday.
Another 477,000 chickens were to be slaughtered near the latest outbreak site by Tuesday, said Lee Sung-jae, a quarantine official at the North Jeolla provincial government.
The Agriculture Ministry issued a nationwide high alert last week to prevent the disease's further spread. South Korea killed 5.29 million poultry in 2003 to halt bird flu, the previous record slaughter.
Seven outbreaks of the deadly virus hit poultry farms across South Korea between November 2006 and March 2007, resulting in the slaughter of about 2.8 million birds.
At least 239 people world-wide have died from bird flu since 2003, according to the World Health Organization. So far, most human cases have been linked to contact with infected poultry.
The disease is relatively difficult for humans to catch, but health authorities fear it could mutate into a form that is easily spread among humans, which could cause a flu pandemic.