SEOUL, Nov. 3 (Yonhap) -- South Korea's antitrust watchdog said Thursday that it has placed 13 more companies on its watch list that limits mutual investments and loan guarantees.

The Fair Trade Commission (FTC) said the number of corporate affiliates on the list stood at 1,618 from 55 business groups as of Tuesday, compared with 1,605 last month.

Twenty-two companies were added to the list from such business groups as KT, Lotte and SK, while nine firms were taken off through mergers or sale of stakes, the watchdog noted.

Under South Korea's fair trade law, affiliates of large business groups with assets of 5 trillion won (US$4.4 billion) or more are restricted from making equity investments or offering loan guarantees in one another.

The rule is aimed at preventing the distortion of conglomerate governance structures.