The Japanese city of Nagasaki is marking 70 years since the dropping of an atomic bomb by the United States.
A ceremony at the Nagasaki Peace Park observed a minute's silence, followed by speeches by the Nagasaki mayor and Prime Minister Shinzo Abe.
A cathedral that was destroyed by the bomb but later rebuilt celebrated a remembrance Mass.
At least 70,000 people died in the attack, which came three days after another bomb was dropped on Hiroshima.
Nagasaki was only chosen because the original target, Kokura, was obscured by a cloud.
A solemn ceremony in front of guests from 75 countries began on Sunday with a declaration read out by children.
A minute's silence and bells marked the time of the explosion at 11:02 (02:02 GMT). Nagasaki mayor Tomihisa Taue then delivered a peace declaration to the ceremony.
In his address to the ceremony, Mr Abe said Japan remained "determined to pursue a world without nuclear weapons".
In a statement read out on his behalf, UN Secretary General Ban Ki-moon said: "Nagasaki must be the last - we cannot allow any future use of nuclear weapons. The humanitarian consequences are too great. No more Nagasakis. No more Hiroshimas."
'Thunder in a clear sky'
The effects of the bomb were instant and devastating. It destroyed a third of the city, killing thousands instantly and condemning more to death from radiation sickness.
Days later, Japan surrendered, ending World War II, although the necessity of the two bombs has been debated ever since.
"It was a clear, sunny day and there was a sudden, blinding flash," remembered one Nagasaki survivor, Toru Mine, who now guides visitors at a museum dedicated to the event.
"My first thought was that it should be a thunder, but I soon realised it's bizarre to have a thunder in a clear sky."
Another survivor, 86-year-old Sumiteru Taniguchi, still bears scars on his back, the remains of three ribs that half rotted after the bomb dropped protruding from his chest.
''While people around me were dying, I lived. People say I survived but I think I was kept alive. I am still suffering," he said.