Nagasaki held a moment of silence at 11:02 a.m. (02:02 UTC/GMT) on Saturday to mark the moment the plutonium bomb named "Fat Man" was dropped by a US bomber over the southern Japanese city 80 years ago.

In a message of peace to the world, twin bells from Urakami Cathedral also rang together for the first time since the bombing on August 9, 1945. One of the bells had gone missing after the attack but was restored by volunteers.

Speaking at the ceremony, Nagasaki Mayor Shiro Suzuki said humanity faced an imminent "existential crisis," warning that the world is plagued with a "vicious cycle of confrontation and fragmentation," Japan's Kyodo News reported.

Prime Minister Shigeru Ishiba, in his speech, vowed to uphold Japan's decades-long commitment of not possessing, producing or permitting the introduction of nuclear weapons.

His government will work to lead global efforts to bring about "a world without nuclear war and a world without nuclear weapons," Ishiba said.

Ishiba made no comment about Japan's refusal to sign or even participate in the Treaty on the Prohibition of Nuclear Weapons. 

Survivors and their families have repeatedly called for Japan to sign the UN treaty, which entered into force in 2021. Japan, as an American ally, says it needs US nuclear possession as deterrence.

Russia, Israel invited to Nagasaki peace ceremony

Some 3,000 people, including representatives from 94 countries and regions, attended the ceremony at Nagasaki Peace Park.

Russia's ambassador to Japan was expected to attend the commemoration event, Japanese media report, as was Israel's ambassador.

Russia and Israel, along with Belarus, were not invited to the 2024 ceremony.

The city decided to adopt a more inclusive approach this year, sending invitations to all nations with diplomatic missions in Japan, according to Kyodo News.

Survivors and their families started paying tribute at the park, as well as at the nearby hypocenter park, hours before the official ceremony.

Hiroshima, Nagasaki only atomic bombs used in wartime

Earlier in the week, Hiroshima marked 80 years since the US dropped an atomic bomb on it.

The attacks on Japan remain the only two times atomic bombs have been used in wartime.

Japan surrendered a few days later on August 15, 1945, ending World War II and the country's nearly half-century of aggression across Asia.

By the end of 1945, it's estimated that the death toll from the uranium bomb detonated over Hiroshima was around 140,000 people. The explosion flattened more than two-thirds of the city.

A further 74,000 people were killed by the plutonium bomb dropped on Nagasaki.

In the years that followed, survivors faced side effects from the radiation, such as leukemia or other cancers and chronic diseases.

Some 99,130 survivors of the two atomic bombs are still alive in Japan, with their average age exceeding 86.

Teruko Yokoyama, an 83-year-old member of a Nagasaki organization supporting survivors, told the AFP news agency it was important to "keep records of the atomic bombing damages of the survivors and their lifetime story."

Edited by Sean Sinico