A court has rejected a damages suit filed by former fishermen and their families who allege the state hid key records showing they were exposed to radiation from the Pacific hydrogen bomb tests conducted by the United States in 1954.

The Kochi District Court on Friday acknowledged the plaintiffs were exposed to radiation from the blasts on Bikini Atoll in the Marshall Islands but denied the state's liability.

"We cannot conclude that the state persistently gave up providing support and conducting health surveys to hide the radiation exposure," said Presiding Judge Osamu Nishimura.