About 200 U.S. residents have filed a lawsuit against Tokyo Electric Power Company Holdings Inc. and a U.S. firm, seeking at least $1 billion (about ¥106 billion) to cover medical expenses related to radiation exposure suffered during the 2011 Fukushima nuclear disaster, the utility has said.

Tepco said Monday that the lawsuit was filed on March 14 with the U.S. federal courts for the Southern District of California and the District of Columbia by participants in the Operation Tomodachi relief effort carried out in the wake of the 3/11 earthquake and tsunami that crippled Tepco's Fukushima No. 1 nuclear plant.

In Operation Tomodachi, which began two days after the natural disasters, the aircraft carrier USS Ronald Reagan and other U.S. military resources and personnel were deployed to deliver supplies and undertake relief efforts at the same time as three reactors at the Fukushima No .1 complex suffered fuel meltdowns.

Many of the plaintiffs are suing Tepco and the U.S. company, whose name was withheld by Tepco, for a second time after a similar suit was rejected by the Californian federal court in January.

They are seeking the establishment of a compensation fund of at least $1 billion to cover medical and other costs, the utility said.

The plaintiffs claim that the nuclear disaster occurred due to Tepco's improper design and management of the plant. They are also seeking compensation for physical and psychological damage suffered as a result of the disaster, the utility said.