The Fair Trade Commission said Friday it has asked a court to halt Rakuten Inc.'s plan to make retailers on its online marketplace shoulder the cost of free shipping amid complaints about the policy.

The antitrust watchdog submitted the request to the Tokyo District Court after opening an investigation last month into whether the e-commerce giant was breaking the antimonopoly law by abusing its dominant position over smaller online merchants that depend on its platform.

The watchdog, which last submitted such a request in 2004, has been stepping up scrutiny of Rakuten and other tech giants, including Google LLC, Amazon.com Inc., Apple Inc. and Facebook Inc., collectively dubbed GAFA, to determine whether they are abusing their market positions.

A group of around 450 merchants has submitted a petition to the FTC claiming Rakuten is using its dominant position to force them to cover free shipping for all orders exceeding ¥3,980 ($36) starting from March 18.

Rakuten President Hiroshi Mikitani said at a news conference earlier this month that his company would go ahead with the plan regardless of the FTC investigation.

He insisted the new policy is essential for Rakuten and retailers on its online marketplace to survive intensifying competition with rivals such as Amazon.com.