Authorities investigated Kansai on suspicion of having prevented competition in the high-voltage power segment in Chubu, Kansai and Chugoku areas, western and central Japan, the utility said in a statement.

"We solemnly accept the raid and we will fully cooperate with the investigation," a company spokeswoman said, without elaborating on the investigation.

Chubu and its unit were also raided on suspicion of violations of the antimonopoly act in the high-voltage electricity market in Chubu and other regions as well as in low-voltage power and city gas markets in the Chubu region, it said in a statement.

Media reports said the utilities had prevented competition by agreeing to not go after each other's high-voltage power customers such as factories and other business owners, thereby preventing price cuts amid deregulation.

(Reporting by Tokyo Newsroom; Editing by Kim Coghill)