Reporter: About 55,000 people attended a ceremony at the city's Peace Memorial Park.
The mayor of Hiroshima city, Kazumi Matsui, made a speech to the gathering calling for world leaders to step up efforts toward global denuclearization.
"I hope that the Japanese government will serve as a bridge between nuclear-capable nations and those without, and be at the forefront of discussions (on nuclear disarmament). And I propose that Hiroshima be the place from which such discussion emanates."
Tourists stopped at various memorials in the park trying to imagine what it was like on that day 70 years ago.
The memorial has stirred deep grief for the rel
