In a somber ceremony in Hiroshima, some 50,000 survivors, relatives of survivors, government officials and foreign delegates observed a moment of silence at 8:15 am local time (2315 GMT), the time when the first atomic bomb to ever be used in war exploded on 6 August 1945, devastating the city and killing tens of thousands of its residents.

Prime Minister Shinzo Abe told the ceremony that, as the only country ever to have faced nuclear attack, Japan had a duty to get rid of nuclear weapons.

The mayor of Hiroshima, Kazumi Matsui, also urged the abolition of nuclear armaments.

"We offer heartfelt consolation to the souls of the atomic bomb victims by pledging to do everything in our power to eliminate the absolute evil of nuclear weapons and achieve a peaceful world," he said.

On 6 August 1945, a US B-29 bomber called Enola Gay dropped an atomic bomb on Hiroshima that killed an estimated 140,000 by December of that year. Three days later, another atomic bomb was dropped on the port city of Nagasaki, killing an estimated 70,000 people there.

The Allied powers argued at the time that the attacks speeded up Japan's surrender and thus the end of the Second World War, preventing millions more casualties from a land invasion planned for later in the year.

Nuclear energy controversy

Matsui went further than Abe, however, in speaking about Japan's policies on nuclear power, which have come into focus since a 2011 earthquake and tsunami damaged a reactor in the city of Fukushima.

He criticised the government for its intentions to restart the country's nuclear plants, shut in the wake of the accident, and for its nuclear exports to other countries.

"We urge the national government to rapidly develop and implement a responsible energy policy that places top priority on safety and the livelihoods of the people," he said.

Victims of the Hiroshima bombing offered their support to those affected by the Fukushima accident, where the situation remains dangerous amid leaks of radioactive water.

Anti-atomic sentiment has gripped the country since the disaster, which spread radiation over a large area and forced thousands to leave their homes.

tj/ipj (AFP, AP, Reuters)