Kyushu Electric Power said it is under the investigation and it will announce information swiftly if necessary.

The Fair Trade Commission declined to comment on a report Friday in The Nikkei the commission has decided to fine three major utility firms including Kyushu Electric Power tens of billions of yen in total for breaching antitrust laws.

The newspaper reported that the regulator will penalise Kyushu Electric Power, Chugoku Electric Power Co and Chubu Electric Power Co for agreeing not to expand in each other's industrial power supply markets.

Any possible penalty would add to financial pain stemming from rising fuel procurement costs as fuel energy prices have soared and the yen has weakened.

(Reporting by Kaori Kaneko and Yuka Obayashi; Editing by David Gregorio)