The Japanese city of Nagasaki on Wednesday marked 78 years since the US dropped the atomic bomb, killing tens of thousands of people in the last days of World War II.

The remembrance ceremony took place amid heavy rains brought to Japan by Tropical Storm Khanun.

The storm prevented Prime Minister Fumio Kishida from attending the ceremony and forced the event to be held indoors for the first time since 1963.

The US dropped the "Fat Man" nuclear bomb on Nagasaki on August 9, 1945 — three days after dropping another atomic bomb on the city of Hiroshima. Japan then surrendered on August 15, officially ending World War II.

Nagasaki remembers the thousands who died

The ceremony held a minute of silence at 11:02 a.m. (0202 GMT), marking the moment the bomb was dropped on the city.

Up to 70,000 people are believed to have been killed in the blast and another 75,000 were injured. The total death toll from both cities and the fallout is estimated to be around 400,000.

Hiroshima and Nagasaki are the only sites to be hit by nuclear bombs in history, outside of tests.

Survivors of the bomb and its radiation effects joined Wednesday's ceremony.

Leaders call for nuclear disarmament

Kishida and UN Secretary-General Antonio Guterres both addressed the ceremony, held in an exhibition hall rather than the Peace Park where it is usually held.

"There is some division in the international community with regards to nuclear disarmament, especially due to the Russian nuclear threat," Kishida said.

"It's becoming more and more difficult to mark a path towards a world without nuclear weapons, but Japan, as the current president of the G7 and a non-permanent member of the UN Security Council, must strengthen the work together with the international community," he added.

Guterres also called for a world free from nuclear weapons.

Nagasaki Mayor Shiro Suzuki, who was in attendance, called on nuclear-armed nations to "show courage" and move away from nuclear deterrence.

ab/sms (dpa, EFE)