HIROSHIMA, Japan (AFP) - Tens of thousands of people gathered in Hiroshima on Thursday to mark 70 years since the atomic bombing that helped end World War II but still divides opinion today over whether the total destruction it caused was justified.
Bells tolled as a solemn crowd observed a moment of silence at 8.15 am local time, when the detonation turned the western Japanese city into an inferno, killing thousands instantly and leaving others to die a slow death with horrible injuries.
Children, elderly survivors and delegates representing 100 countries were in attendance with many placing flowers in front of the cenotaph at Peace Memorial Park in downtown Hiroshima.
Prime Minister Shinzo Abe, United States ambassador Caroline Kennedy, and Undersecretary for arms control Rose Gottemoeller, the most senior Washington official ever sent to the service, were in attendance.
"As the only country ever attacked by an atomic bomb... we have a mission to create a world without nuclear arms," Mr Abe told the crowd. "We have been tasked with conveying the inhumanity of nuclear weapons, across generations and borders."
The Premier said his country would submit a fresh resolution to abolish nuclear weapons at the UN general assembly later this year.
The now-bustling city's mayor Kazumi Matsui said nuclear weapons were an "absolute evil" as he urged the world to put an end to them forever.
"To coexist we must abolish the absolute evil and ultimate inhumanity that are nuclear weapons. Now is the time to start taking action," he said in his annual speech.
An American B-29 bomber named Enola Gay dropped an atomic bomb, dubbed "Little Boy", on Hiroshima on Aug 6, 1945.
Nearly everything around it was incinerated, with the ground level hit by a wall of heat up to 4,000 deg C - hot enough to melt steel.
"It was a white, silvery flash," Hiroshima survivor Sunao Tsuboi, 90, told AFP before Thursday's memorial.
"I don't know why I survived and lived this long. The more I think about it... the more painful it becomes to recall."
About 140,000 people are estimated to have been killed in the attack, including those who survived the bombing itself but died in the folllowing days, weeks and months from severe radiation exposure.
On Aug 9, the port city of Nagasaki was also attacked with an atomic bomb, killing more than 70,000 people.
Japan surrendered days later - on Aug 15, 1945 - bringing the war to a close.
Mr Abe laid a wreath at the ceremony attended by US ambassador to Japan Caroline Kennedy and other officials.
Under-secretary for arms control Rose Gottemoeller was also scheduled to attend, the most senior US official sent from Washington to the annual memorial.
Opinion remains divided over whether the twin attacks were justified.
While some historians say that they prevented many more casualties in a planned land invasion, critics have said the attacks were not necessary to end the war, arguing that Japan was already heading for imminent defeat.
Dropping the bombs, which were developed under strict secrecy, was hugely popular with war-weary Americans at the time - and 70 years on, a majority today still think it was the right thing to do.
Fifty-six per cent of Americans surveyed by the Pew Research Centre in February said using the atomic bomb on Japanese cities was justified, compared to 79 per cent of Japanese respondents who said it was not.
Mr Paul Tibbets, who piloted the Enola Gay, said he never had any second thoughts about dropping the bomb, telling a newspaper in an interview in 2002, five years before his death: "I knew we did the right thing."
Washington, which has been a close ally of Tokyo since the war, has never officially apologised for the bombings.
Leaked diplomatic cables from 2009 suggested that the Japanese government had rebuffed the idea of a US apology and a visit to Hiroshima by President Barack Obama.
But US diplomats have regularly attended the annual commemorations, and three years ago, a grandson of former US President Harry Truman, who gave the order to drop the bombs, attended peace ceremonies in Hiroshima.
This year's memorial comes just days ahead of the scheduled restart of a nuclear reactor in southern Japan - the first one to go back on line after two years of complete hiatus following the tsunami-sparked disaster at Fukushima in 2011.
While Mr Abe's government has pushed to switch reactors back on, public opposition to atomic power remains high after Fukushima, the world's worst nuclear accident since Chernobyl in 1986.
Mr Abe, a strident nationalist, has also been criticised at home for his efforts to expand the role of pacifist Japan's Self-Defense Forces, changes that could open the door to putting troops into combat for the first time since the end of the war.
The moves caused a fresh stir as Defense Minister Nakatani admitted on Wednesday that new security laws being debated in Parliament could - in theory - allow for Japan to transport nuclear weapons to allies.
He quickly dismissed that idea as unlikely, however.