Japan's prime minister, marking the 66th anniversary of the bombing of Hiroshima, said his country is "working toward a society with a reduced dependence on nuclear energy."
Naoto Kan used Saturday's memorial ceremony to touch on the subject of nuclear safety in light of radiation threats from the Fukushima Daiichi nuclear power plant, which was severely damaged in the massive quake and tsunami that hit northeastern Japan earlier this year.
"We will deeply reflect over the conventional belief that nuclear energy is safe, thoroughly look into the cause of the accident and — to secure safety — implement fundamental measures," he said.
Bombing survivors, dignitaries and residents attended the ceremony near the gutted Atomic Bomb Dome to observe a moment of silence, broken only by the ringing of a special peace bell.
About 140,000 people were killed or died within months when the American B-29 Enola Gay bombed the city on Aug. 6, 1945. Three days later, about 80,000 people died after the United States attacked Nagasaki. Japan surrendered on Aug. 15, ending the Second World War.
Hiroshima Mayor Kazumi Matsui, a son of an atomic bomb survivor, also spoke to the crowd about the crisis in Fukushima and called on the government to review its nuclear policy.
He said the crisis has traumatized the public and that Tokyo needed to act to regain public trust.
"Since the Fukushima Daiichi nuclear accident has occurred the continued and ongoing fear of radiation has generated anxiety among those in the affected area and many others," he said. "The trust the Japanese people once placed in nuclear power has been shattered."
Matsui stopped short of calling for a nation without nuclear power, while reiterating his pledge to work toward a world without atomic weapons.
Japan has long vowed never to make or possess nuclear weapons, but embraced nuclear power as it aimed to rebuild and modernize after the war.