They listened in silence as a bell tolled at 8:15 exactly -- the moment, 60 years ago, when the U.S. bomber "Enola Gay" dropped its atomic bomb over the city.
Some 140,000 people in Hiroshima were killed instantly in the explosion or in the months afterward. Many survivors had horrific burns, or suffered from the effects of radiation.
In Japanese, these and other nuclear bomb survivors are called "Hibakusha," or "bomb-affected people."
In a speech read in his name, UN Secretary-General Kofi Annan said, "Today, we are all Hibakusha."
In his speech, Hiroshima Mayor Tadatoshi Akiba pleaded for peace and a nuclear-weapon-free world. And Prime Minister Junichiro Koizumi made a similar call.
"We are committed with all our efforts to lead the international community to prevent nuclear proliferation, scrap nuclear arms, and bring about an end of nuclear weapons," Koizumi said.
But the ceremony remembered not only Japan's atomic bomb victims. Yohei Kono, the speaker of parliament's lower house, linked the bombing to Japan's own military past.
Kono said Japan could have helped Asian nations but instead deprived Korea of its independence and invaded China -- actions for which Japan's neighbors say Tokyo still has not done enough to apologize.
"On the epitaph in the Peace Park it is carved: 'Rest in Peace as we will not make the same mistake twice.' But what is that mistake? One is that our country since the end of the Meiji Restoration [restoration of imperial rule in the 19th century] until 60 years ago when the atom bomb was dropped, were off-track in Asia and walked the path to war," Kono said.
The bombing of Hiroshima was considered by many to be crucial in ending World War II. Japan agreed to surrender to the Allies a few days later, after the United States bombed another Japanese city, Nagasaki. But it's still controversial, and critics say more could have been done to negotiate an end to the war.
For survivors, their greatest mission is to keep memories of the bombing alive. But that's getting harder. Survivors' average age is now over 73 and numbers are dwindling. And even among victims, one survivor said, the anger towards nuclear weapons is waning as time goes on.
(compiled from agency reports)
See also: For One Hiroshima Survivor, A Journey From Hate To Reconciliation
60 Years Later, Nagasaki Bomb Witness Is Finally Heard