South Korea's antitrust regulator said Wednesday it has decided to impose a combined fine of 25.1 billion won ($21.2 million) on seven poultry-processing companies for colluding to fix prices of chickens.

Harim Co. and six other companies colluded to fix prices and supplies of chickens to be used for "samgyetang," or Korean ginseng chicken soup, between July 2011 and July 2017, according to the Korea Fair Trade Commission (KTFC).

Their price fixing led to a hike of chicken prices during summer when demand remains high, while preventing chicken prices from falling during off-seasons, the commission said.

Harim will be tentatively slapped with the largest fine of 7.87 billion won, followed by 5.17 billion won for Orpum Co. The regulator plans to file a complaint with the prosecution against the two firms.

The KFTC also ordered the seven firms to take corrective measures. (Yonhap)