A bell tolled as thousands of people, including ageing survivors and relatives of victims, observed a minute's silence at 11:02 am (02:02 GMT), the exact moment the the blast occurred, killing 74,000 people in Nagasaki on August 9, 1945.

The bomb was dropped three days after the first atomic bomb dropped by the US B-29 bomber Enola Gay was detonated over the western Japanese city of Hiroshima.

The two cities saw renewed international attention this year after Barack Obama, became the first sitting US president to visit the site of the nuclear attack in Hiroshima in May.

Representatives from 53 countries, in addition to the UN and EU, attended the ceremony at the city's Peace Park and paid tribute to victims of the attack.

Calls for peace

"Now is the time for all of you to bring together as much of your collective wisdom as you possibly can, and act so that we do not destroy the future of mankind," Mayor Tomihisa Taue said in his peace declaration.

The mayor also criticized Japan's central government for what he called its "dependence" on the US for nuclear deterrence while at the same time advocating the abolition of nuclear weapons. He urged Tokyo to enshrine into law its three non-nuclear principles of not producing, possessing or allowing nuclear weapons on Japanese territory. These are currently non-binding.

Japanese Prime Minister Shinzo Abe, in his address in Nagasaki, called on world leaders to honor the global Nuclear Non-proliferation Treaty. "We must not allow a repeat of the horrible experiences of Hiroshima and Nagasaki that happened 71 years ago," Abe said.

jbh/kl (dpa, AFP)