Five companies including Mercedes-Benz Korea, Jaguar Land Rover Korea Co., and Nissan Korea Co. had provisions that kept clients from scrapping their purchase contracts and getting a refund.

Three firms, including Audi Volkswagen Korea, did not return money to customers who had free maintenance coupons that had already expired, while four businesses prohibited clients from selling their coupons.

The watchdog said all related companies have revised the terms to let South Korean customers cancel the contract and get a refund if they want.

"We expected that the revision will help reduce disputes over contract cancellations and refunds in imported car purchases," the FTC said in a release.

The imported car market in South Korea has been on a roll for years on the rising demand for luxury European sedans.

Sales of imported cars in South Korea jumped 24.2 percent to 243,900 in 2015 but fell slightly to 225,279 in 2016 due mainly to Volkswagen's emissions scandal. (Yonhap)