South Korea remained on alert over a further rise in highly pathogenic bird flu cases Friday as the number of highly pathogenic cases in farms approached 10 in less than two months.

The country reported this year's ninth case of highly pathogenic bird flu from a duck farm in Jangseong, about 250 kilometers south of Seoul, according to the Ministry of Agriculture, Food and Rural Affairs. It was also the fourth case from South Jeolla Province.

Local authorities are investigating another suspected case of highly pathogenic bird flu from a duck farm in Jeongeup, about 220 kilometers south of Seoul.

South Korea has been reporting seriously contagious avian influenza cases from local farms nationwide, also including the provinces of Gyeonggi, North Chungcheong, North Gyeongsang and North Jeolla.

"Bird flu cases traced to poultry farms will put a significant burden on society," Prime Minister Chung Sye-kyun said.

"We need to thoroughly investigate infected farms and take prompt actions to prevent additional cases," Chung added, pointing out the country is at a critical juncture in curbing the nationwide spread of the disease.

The prime minister also ordered authorities to focus their disinfection operations on wild bird habitats surrounding poultry farms.

The country has already completed the culling of more than 4.4 million poultry being raised at affected farms, including 2.65 million chickens and 1.01 million quails, according to the ministry.

Authorities cull poultry within a 3-km radius of infected farms as a preventive measure.

Highly pathogenic avian influenza is contagious and can cause severe illness and even death in poultry.

The country reported its first highly pathogenic case in 32 months in late October in Cheonan, 92 kilometers south of Seoul, from wild birds.

Since then, a total of 23 cases have been found from wild bird habitats across the country, according to the ministry. Authorities are investigating two more suspected cases among wild birds. (Yonhap)