South Korea's agricultural ministry said Thursday it has confirmed four additional cases of highly pathogenic bird flu, raising concerns over the further spread of the disease in the country.

Of the new cases, one case each was confirmed in Pocheon, Paju, Icheon, and Anseong the previous day, all in Gyeonggi Province that surrounds the capital city, according to the Ministry of Agriculture, Food and Rural Affairs.

A seven-day standstill order has been issued on all poultry farms in the four areas.

South Korea reported its first H5N8 strain of avian influenza from local farms in nearly three years back in November.

Gyeonggi Province that surrounds Seoul reported 24 cases, with the provinces of North and South Jeolla accounting for 14 cases each.

Authorities are investigating two separate suspected cases from Anseong and Gochang, 296 kilometers south of Seoul, as well.

The country has culled 23 million poultry so far under its policy of destroying all birds within a 3-kilometer radius of infected farms.

The average consumer price of eggs has shot up 27.7 percent over the past week from a year earlier. Those of chicken and duck meat have gained 14.6 percent and 33.9 percent, respectively.

From wild birds, the total caseload of highly pathogenic avian influenza reached 105.

South Korea reported a whopping 340 cases of the H5N8 strain of avian influenza traced to poultry farms from October 2016 to January 2017. (Yonhap)