Kazumi Matsui, right, mayor of Hiroshima, and the family of the deceased bow before they place the victims list of the Atomic Bomb at Hiroshima Memorial Cenotaph during the ceremony to mark the 75th anniversary of the bombing at the Hiroshima Peace Memorial Park, Aug 6, 2020. (PHOTO / AFP)

TOKYO - Japan marked the 75th anniversary of the atomic bombing of Hiroshima on Thursday, with its mayor urging the world to unite against threats to humanity including those from nuclear weapons.

Hiroshima Mayor Kazumi Matsui said countries should "put aside their differences and come together to overcome both man-made and natural challenges."

"Civil society must reject self-centered nationalism and unite against all threats," Matsui said at the annual ceremony at Peace Memorial Park.

The memorial ceremony was scaled down due to a resurgence of COVID-19 infections in Japan and the need to maintain social distancing.

Civil society must reject self-centered nationalism and unite against all threats.

Kazumi Matsui, Hiroshima Mayor

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A moment's silence was observed by those in attendance, including Japanese Prime Minister Shinzo Abe, at 8:15 am local time, the time when the "Little Boy" uranium-core atomic bomb dropped by a US bomber exploded above Hiroshima on Aug 6, 1945.

The bomb killed around 140,000 people by the end of 1945.

Despite Japan not being a signatory to the Treaty on the Prohibition of Nuclear Weapons, Abe, in his speech, said countries must not let nations' different stances on nuclear weapons widen further.

"Each country must step up efforts to remove a sense of mistrust through mutual involvement and dialogue amid the severe security environment and widening differences between nations' positions on nuclear disarmament," the Japanese premiere said.

Kazumi Matsui, right, mayor of Hiroshima, and the family of the deceased bow before they place the victims list of the Atomic Bomb at Hiroshima Memorial Cenotaph during the ceremony to mark the 75th anniversary of the bombing at the Hiroshima Peace Memorial Park, Aug 6, 2020. (PHOTO / AFP)

READ MORE: Hiroshima marks 73rd anniversary of atomic bombing in WWII

The number of survivors of the two atomic bombings including Nagasaki known as hibakusha with an average age of 83.31, have dropped by 9,200 from a year earlier to 136,682 as of March, according to the Ministry of Health, Labor and Welfare.

While Japan commemorates the tragedies it had experienced at the end of World War Two, historians and political minds of the international community have encouraged Japan to come to see themselves not as merely victims of the atomic bombings but also as the perpetrators who led to these tragic incidents to happen in the first place.

Japan brutally occupied many parts of Asia before and during World War II, causing untold suffering and deaths to hundreds of thousands of innocent victims. 

A girl walks past a mosaic made of paper cranes for the victims of the 1945 Atomic bomb near Hiroshima Peace Memorial Museum in Hiroshima, western Japan, Aug 4, 2020. (PHOTO / AP)

The United Nations called on the international community to make efforts to create a future free from the nuclear threat. "Seventy-five years ago, a single nuclear weapon visited unspeakable death and destruction upon this city," UN Secretary-General Antonio Guterres said in his video message.

"There truly is no winner in a nuclear war," Tijjani Muhammad-Bande, president of the UN General Assembly, also said in a video message, reports Xinhua from United Nations.

A man rests on one of the chairs for the Peace Memorial Ceremony placed at intervals to help protect against the new coronavirus at the Hiroshima Peace Memorial Museum in Hiroshima. (PHOTO / AP)