Tens of thousands of people at an annual ceremony in Hiroshima's Peace Memorial Park observed 60 seconds of silent prayer at 8:15 a.m. the minute that the United States dropped the bomb on Aug. 6, 1945. City officials estimated the crowd at 30,000 to 50,000.
Those attending the ceremony bowed their heads amid sadness for the 140,000 who perished and disappointment that two world wars and countless other conflicts in the 20th century failed to bring an end to hatred.
"The end of the century of war has not automatically ushered in a century of peace and humanity," Hiroshima Mayor Tadatoshi Akiba told gatherers. "Our world is still darkened not only by the direct violence of civil wars, but also by innumerable other forms of violence."
A choir of children sang a song of peace at the ceremony, which is televised nationally each year. Hiroshima is about 425 miles southwest of Tokyo.
On Thursday, ceremonies were to be held to mark the atomic bombing of Nagasaki, farther south, in which 70,000 people were killed. Japan surrendered on Aug. 15, 1945, ending World War II.
Amid growing concern that tensions between India and Pakistan the world's newest nuclear powers and the illegal sales of nuclear weapons to so-called rogue nations could lead to atomic war, Prime Minister Junichiro Koizumi said he would redouble efforts to achieve a worldwide ban on testing of atomic weapons.
"As the only country that has experienced a nuclear attack we have appealed to the global community to eradicate nuclear weapons and build a lasting peace, so that the devastation of nuclear warfare will never again be repeated," Koizumi said.
While the 1945 atomic bombings have largely become relegated to events of history in the minds of many people around the world, Japan still grapples with the aftermath of the raids over Hiroshima and Nagasaki.
Courts continue to hear lawsuits filed by survivors who say they have not received sufficient medical care for ailments caused by exposure to radiation.
Also, Japanese have yet to resolve questions over their own destructive role in World War II. Many feel that Japan should apologize to neighboring countries in Asia and in the Pacific for what they call reckless military expansion before and during the war.
South Koreans have sharply criticized a Japanese middle-school textbook that critics claim whitewashed wartime atrocities committed by the Japanese military.
According to Kyodo News agency, representatives from seven Hiroshima prefectural organizations of atomic bomb survivors on Mondaurged Koizumi not to carry out promises to pay his respects on Aug. 15 to the nation's war dead at Tokyo's Yasukuni Shrine to many a symbol of Japan's wartime aggressions as it was used to encourage militarist fervor during the early 20th century.
Koizumi said during his campaign that he would make the visit.
Elsewhere, anti-nuclear activists marked the Hiroshima anniversary with protests and direct action. Two anti-nuclear activists were arrested at a British naval base after they swam into a high-security area where submarines armed with Trident nuclear missiles are berthed, naval officials said.
The activists, from an antinuclear arms group called "Trident Ploughshares," were arrested in the early hours while spray-painting the word "ILLEGAL" on to the side of a submarine at the Faslane naval base near Dunbarton in Scotland.
But a spokeswoman at the base said no paint had been found on the submarine. "They didn't get on board any submarines and they didn't do any damage," she said.
Britain has four Trident submarines.
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