A minute's silence was declared at 8:15 a.m. sharp (11:15 p.m. Sunday GMT), which was the exact time the U.S. dropped the Little Boy bomb on Hiroshima 62 years ago. About a hundred white doves, a symbol of peace, were released into the air accompanied by tolling bells.
A list containing the names of 5,221 people who survived the bombing but died over the past year were placed on the park's memorial cenotaph. The total number of victims has reached 253,000.
The ceremony gathered 42 ambassadors, including Ambassador Mikhail Bely of Russia - the only nuclear power represented at the event.
Japanese Prime Minister Shinzo Abe addressed the ceremony. "We must repeat our commitment to the Three Non-Nuclear Principles, to peace in the world and to the Constitution," he said.
The Three Non-Nuclear Principles are part of Japan's new nuclear policy adopted in the late 1960s in the form of a parliamentary resolution. The principles say "Japan shall neither possess nor manufacture nuclear weapons, nor shall it permit their introduction into Japanese territory."
The Japanese premier promised human rights advocates Sunday that the government would revise the disputed criteria for qualifying people as victims of the nuclear bombings. The current norms often leave people without any compensation.
Abe also apologized for a statement by former defense minister, Fumio Kyuma, who said in late June that the dropping of atomic bombs by the U.S. "could not be helped" as it was aimed at preventing the Soviet Union from entering the war against Japan.
The second nuclear bomb was dropped on Japan's Nagasaki August 9, 1945.
