South Korea's agricultural ministry said Wednesday it has identified this year's 20th highly pathogenic bird flu case from farms, amid deepening concerns over the nationwide spread of the contagious disease.

The latest case was reported at a duck farm in Yongin, just south of Seoul, according to the Ministry of Agriculture, Food and Rural Affairs.

South Korea has reported farm-related highly pathogenic bird flu cases across the nation since late November, including one case from a guest ranch.

Officials also launched investigations into suspected cases from a duck farm in North Chungcheong Province, along with another egg farm in Hwaseong, which also lies south of the capital city.

On Wednesday, a new suspected case was also reported from a farm that is raising 40,000 ducks in Namwon, North Jeolla Province.

Earlier in the day, the country issued a standstill order in Gyeonggi Province that surrounds Seoul, along with the central city of Sejong and adjacent provinces of Chungcheong.

The 24-hour order, which will run through 1 a.m. Thursday, will ban travel of all livestock, workers and automobiles at poultry farms in the regions.

Violators of the standstill order will face up to one year in prison or fines of 10 million won ($9,000).

South Korea reported this year's first highly pathogenic avian influenza case from wild birds in late October. A total of 35 cases were confirmed from wild bird habitats across the country.

The country, meanwhile, has culled 6.3 million poultry as of Tuesday.

Under local law, poultry within a 3-km radius of a farm infected with highly pathogenic cases must be destroyed. (Yonhap)