Hiroshima is commemorating the 70th anniversary of the first atomic bomb being dropped by a US aircraft.
A ceremony, attended by Prime Minister Shinzo Abe, was held at Hiroshima’s memorial park before thousands of lanterns are released on the city’s Motoyasu river.
The bombing – and a second one on Nagasaki on August 9 – is credited with bringing to an end World War II.
It claimed the lives of at least 140,000 people in Hiroshima.
A US B-29 bomber called the Enola Gay dropped the uranium bomb, exploding some 1,800ft above Hiroshima, at around 08:10 on August 6, 1945.
People across Japan have observed a minute’s silence to mark the anniversary. In Hiroshima a bell tolled at 08:15 local time – when the US aircraft dropped the bomb that flattened the city centre.
Addressing 40,000 people who attended the commemoration ceremony at Hiroshima’s peace park near the epicenter of the 1945 attack, Shinzo Abe called for worldwide nuclear disarmament.
The prime minister said that that atomic bomb not only killed thousands of people in Hiroshima but also caused unspeakable suffering to survivors.
“Today Hiroshima has been revived and has become a city of culture and prosperity.
“Seventy years on I want to reemphasize the necessity of world peace,” he said.
Shinzo Abe and Hiroshima Mayor Kazumi Matusi were joined by US Ambassador to Japan Caroline Kennedy for the official ceremony of remembrance on August 6, which included silent prayers, the release of doves and a declaration of peace.
Kazumi Matsui described nuclear weapons as an “absolute evil” while urging the world to put an end to them forever.
“To coexist we must abolish the… ultimate inhumanity that is nuclear weapons. Now is the time to start taking action,” he said in his annual speech.
Later in the day, thousands of paper lanterns will be released on the city’s Motoyasu River – symbolizing the journey to the afterlife of those who died.
The Hiroshima bombing commemoration comes as divisions in Japan rise over Shinzo Abe’s bid to pass unpopular legislation to expand the country’s military role worldwide.