US Secretary of State John Kerry said Monday he was "deeply moved" by his visit earlier in the day to the Hiroshima atomic bomb memorial in the Japanese city, AFP reports.

"I want to express on a personal level how deeply honored I am, how deeply moved I am to be the first US secretary of state to visit the memorial," he told reporters.

He described the memorial as "extraordinary" and called it a "gut-wrenching display that tugs at all your sensibilities as a human being".

Kerry was the highest-ranking US administration official to pay respects at the spot where American planes launched the world's first nuclear attack, in 1945.