TOKYO -- Amazon Japan's offices were raided by Japan's anti-monopoly watchdog agency on suspicion of having unfairly forced retailers to favor its e-commerce website over rival sites, sources close to the matter told the Nikkei on Monday.

The Japan Fair Trade Commission recently conducted an on-site inspection of the Japanese arm of the U.S. online retail giant, amid suspicion the company may have required vendors on its site to set prices for their products lower than on other sites.

Provisions in the country's anti-monopoly act prohibit companies from unfairly restricting the activities of others with whom they have a business relationship.

A spokesperson for Amazon Japan declined to comment.

(Nikkei)