Tokyo Electric Power Co. began charging some of its corporate customers higher electricity rates Sunday as the cost of fueling thermal power plants soars amid the fallout from its nuclear disaster at the Fukushima No. 1 complex.

However, only 11,000 of Tepco's 237,000 corporate customers had agreed to the hikes as of March 22. The utility also is under fire for failing to tell customers, unless they ask, that they can refuse the rate hike if their contracts have not yet expired.

Many resisting the rate hikes have complained about a lack of clarity in Tepco's reasoning and about its insufficient explanations.