Moody's Japan K.K. said Thursday it has downgraded both its senior secured rating and long-term issuer rating on Tokyo Electric Power Co. by three notches, from A-1 to Baa-1, effective the same day.

The rating actions reflect huge financial burdens on the utility in the wake of the devastating March 11 earthquake and tsunami that have crippled its Fukushima No. 1 nuclear power plant.

The Japan unit of the major U.S. credit rating agency said it will continue reviewing its ratings on the company for possible downgrades.