August 6, 2020: Japan on Thursday marked 75 years since the world's first atomic bomb attack.

But memorial events were scaled back this year because of the pandemic.

Early on Thursday, Japan's Prime Minister Shinzo Abe and the mayor of Hiroshima joined bomb survivors and descendants in the city's Peace Park.

But the general public was kept away, with the ceremony instead broadcast online. Participants, many of them dressed in black and wearing face masks, offered a silent prayer at exactly 8:15 am (2315 GMT Wednesday), the time the first nuclear weapon used in wartime was dropped over the city.

Speaking afterwards, Hiroshima mayor Kazumi Matsui warned in an address that the world must come together to face global threats, like the coronavirus pandemic, and to warn against the nationalism that led to World War II.

"We must never allow this painful past to repeat itself. Civil society must reject self-centred nationalism and unite against all threats," he said.

Humanity must "unite against threats to humanity and avoid repeating our tragic past," Matsui added, making an annual call for a world without nuclear weapons.

In a video message, UN Secretary General Antonio Guterres called on all nations to renew efforts to abolish such weapons.

"Division, distrust and a lack of dialogue threaten to return the world to unrestrained strategic nuclear competition," he said.

"The only way to totally eliminate nuclear risk is to totally eliminate nuclear weapons."

On 6 August 1945, a US bomber dropped the uranium bomb above the city, killing around 140,000 people. 

Three days later a second nuclear weapon was dropped on Nagasaki. Two weeks later Japan surrendered, ending World War Two.