South Korea said Monday that it has expanded disinfection operations at major wild bird habitats and poultry farms to cope with the rising number of highly pathogenic bird flu cases.

"Due to the influx of migratory birds into the country, contaminants can get into local farms at anytime," the Ministry of Agriculture, Food and Rural Affairs said in a statement.

"As we are facing a grave situation, there will be zero tolerance of any violation of the quarantine guidelines," it added.

Local authorities are using 958 units of vehicles and drones to carry out disinfection operations in surrounding areas of poultry farms.

The agricultural ministry also advised farms to apply disinfectants around their farms and clean floors on a daily basis. They are also requested the changing of shoes when moving among sheds.

The country has so far reported 18 highly pathogenic bird flu cases from poultry farms, including at a private park, since late November. No suspected cases were under investigation as of early Monday.

The virus has especially spread at a faster pace in South Jeolla Province, which accounted for six infections. Four were from North Jeolla Province.

The spread of the virus has led authorities to cull 6.1 million poultry so far, including 4 million chickens and 1.2 million quails.

Under local law, poultry within a 3-kilometer radius of farms infected with highly pathogenic cases must be destroyed.

The country reported this year's first highly pathogenic avian influenza case from wild birds in late October. A total of 30 cases was confirmed from wild bird habitats across the country.

The ministry, meanwhile, said the latest cases of bird flu have had only a limited impact on the local market for poultry and eggs.

"The price of eggs has recently increased around 7.3 percent compared to the yearly average," the ministry said, pointing out that retailers also have sufficient volumes of poultry products in stock. (Yonhap)