South Korea's antitrust watchdog said Wednesday that it has slapped a combined 3.3 billion-won ($3.04 million) fine on seven large advertising firms for unfair subcontracting practices.

A probe, which started in the summer of 2013, showed the companies intentionally did not sign formal contracts, putting off payment for services rendered by partners and not providing clearing fees for promissory notes issued, according to the Fair Trade Commission.

All the violators -- Cheil Worldwide, Innocean Worldwide Corp., SK Planet, HS Ad, Daehong Communications, Hancomm and Oricom -- were affiliates of the country's largest conglomerates, such as Samsung, Hyundai Motor, SK, LG and Lotte.

The firms failed to sign or delayed signing formal contracts and did not pay subcontractors in a timely manner as stipulated by the law, the watchdog said.

By firm, Cheil was fined 1.21 billion won, followed by 645 million won for Innocean and 617 million won for Daehong. Others were slapped with fines ranging from 40 million won for Oricom to 588 million won for SK Planet.

The corporate regulator said its actions marked the first time that it screened local advertisement firms for fair trade violations. It said the move will compel companies to follow the law and not take actions that can hurt subcontractors. (Yonhap)