Hiroshima has marked the 76th anniversary of the world's first atomic bombing with the city's mayor urging global leaders to unite to eliminate nuclear weapons, just as they have united against the coronavirus.

Mayor Kazumi Matsui also again demanded that Japan sign the Treaty on the Prohibition of Nuclear Weapons, which took effect in January after years of effort.

"Nuclear weapons, developed to win wars, are a threat of total annihilation that we can certainly end, if all nations work together," Matsui said. "No sustainable society is possible with these weapons continually poised for indiscriminate slaughter."

The treaty notably lacks the U.S. and other nuclear powers as well as Japan.

The U.S. dropped the world's first atomic bomb on Aug. 6, 1945, destroying Hiroshima and killing 140,000 people. It dropped another atomic bomb on Nagasaki three days later, killing another 70,000 people.

The two bombs prompted Japan's surrender, bringing an end to World War II.

Thursday's ceremony at the Hiroshima Peace Memorial Park was significantly scaled-down amid the coronavirus pandemic and was eclipsed by the Olympics in Tokyo.