SEOUL (AFP) - Another bird flu case was found in the South Korean capital Sunday, the Agriculture Ministry said, while it was reported an outbreak in the country's second largest city was caused by the H5N1 strain. More than 8,000 ducks and chickens were immediately culled at an illegally-run farm in Seoul's southeastern district of Songpa after tests showed the potentially deadly virus, the Ministry said. It was later reported by Yonhap news agency that the H5N1 strain had been found in the southeastern port city of Busan. Yonhap added that officials highlighted a possible outbreak on Thursday, which was confirmed by national quarantine agencies on Sunday. Some 6.8 million chickens and ducks have been slaughtered nationwide since the country's latest bird flu outbreak was reported on April 1 but some 36 cases have still been reported across most of the country. No human infections have been confirmed in the current outbreak, or in a previous one between November 2006 and March last year. Health officials Saturday decided to double the stockpile of antiviral flu medicine Tamiflu to 2.5 million treatment courses. The first case in Seoul, a city of some 10 million, was reported last Monday at an aviary in the eastern district of Gwangjin. Quarantine officials quoted by Yonhap news agency said they believe the two cases in the city can be traced to the same traditional market just south of the capital. The government has said it will ban the trade of live chickens and ducks at traditional markets. The H5N1 strain has killed more than 240 people worldwide since late 2003.