HIROSHIMA, Japan - The tolling of a lone bell Sunday amid the summertime drone of cicadas, and then the voices of singing children, marked the day 55 years ago when the United States unleashed ''hell on earth'' on the people of Hiroshima.
Sixty seconds of silent prayer commenced at 8:15 a.m. - the moment that a U.S. B-29 bomber dropped an atomic bomb on the city on Aug. 6, 1945.
Many of the estimated 30,000 to 50,000 people in Peace Memorial Park bowed their heads, some fingering Buddhist prayer beads in the muggy heat.
''It has been precisely 55 years since one single atomic bomb created a hell on earth,'' Mayor Tadatoshi Akiba said in the city's annual peace declaration. ''Unfortunately, our most fervent hope, to see nuclear weapons abolished by the end of this century, has not been realized.''
Fifteen hundred doves were released into the sky at the ceremony, which is televised nationally every year. Three hundred children sang a song of peace.
The bomb killed about 140,000 people. Three days later, the United States dropped a second atomic bomb on Nagasaki, killing 70,000 people. Japan surrendered on Aug. 15, 1945, ending World War II.
Last year, Associated Press media subscribers voted the bombing of Hiroshima and Nagasaki the top news story of the 20th century.
Hiroshima announced Saturday that the names of 5,021 people who were in the city on the day of the bombing and who have died since last year's anniversary were added to a monument dedicated to the victims.
The number of names on the cenotaph in the city about 430 miles southwest of Tokyo now stands at 217,137.
At the ceremony, Prime Minister Yoshiro Mori expressed his ''deepest sympathy'' for those killed. ''My heart also goes out to the people who to this day continue to suffer from the aftereffects of their exposure to radiation.''
After the ceremony, a man crossed a security line, ran toward the lead car of Mori's motorcade and was arrested, said Masashi Watanabe, a spokesman for the Hiroshima prefectural police.
Mori, in the second car, was unharmed.
The man was not carrying a weapon, Watanabe said, and has remained silent in police custody, refusing to give his name and motive.