Japan is marking the 65th anniversary of the world's first atomic bomb attack, with the United States and other major nuclear powers attending for the first time.
The ceremony began Friday morning in Hiroshima with the ringing of bells and the release of doves.
U.N. Secretary General Ban Ki-moon was among the dignitaries who spoke at the ceremony, becoming the first U.N. chief to ever attend the annual event. Mr. Ban called for an elimination of nuclear weapons, reaffirming a pledge he made Thursday in Nagasaki, the target of the second U.S. atomic bomb attack.
The U.S. was represented by Ambassador to Japan John Roos, who did not address the crowd. The U.S. Embassy in Tokyo released a statement saying Roos attended to "express respect for all the victims" of the war.
U.S. Secretary of State Hillary Clinton said Thursday that it was "appropriate" for Roos to attend the memorial because President Barack Obama is committed to a world without nuclear weapons.
Diplomats from Britain and France also attended the ceremony.
Japanese Prime Minister Naoto Kan said the survivors of the nuclear attacks should be "special ambassadors" for denuclearization to remind humanity "not to repeat the horror and misery" caused by the bombings.
The start of the ceremony Friday coincided with the precise moment that the United States dropped an atomic bomb on Hiroshima on August 6, 1945, killing an estimated 140,000 people. Another 70,000 died when a second bomb was dropped on Nagasaki three days later. Japan surrendered unconditionally on August 15, bringing an end to World War Two.