People in Japan are remembering the victims of one of history's most catastrophic war events, 78 years after a US warplane dropped an atomic bomb on the city of Hiroshima.

People gathered at the city's Peace Memorial Park to honor the victims in the early morning hours.

One woman who was two-years-old when the bomb was dropped said, "I've been coming here for decades to pay my respect to my relatives who have died. I'm already old and I wonder how many more times I'll be able to come."

"I come here every year with my family to tell my children this anniversary is very meaningful," said a 41-year-old man.

His nine-year-old daughter said, "I wish for a peaceful world."

Hiroshima fell silent at 8:15 a.m. on Sunday morning, the exact moment the bomb exploded on August 6, 1945. The heat rays, radiation and blast wave from the bombing devastated the city, killing about 140,000 people by the end of that year. Many who survived suffer from cancer and other diseases related to their exposure to radiation.

About 50,000 people attended this year's ceremony. Some seats were open to the public for the first time in four years, as coronavirus measures have been eased.

Hiroshima Mayor Matsui Kazumi placed a list of the names of 339,227 victims in a cenotaph. It includes 5,320 people who have died or whose deaths have been confirmed over the past year.

In his peace declaration, the mayor noted that G7 leaders reaffirmed their commitment to achieving a world without nuclear weapons when they gathered in his city in May.

But he pointed out the leaders also said that their security policies are based on the understanding that, as long as they exist, nuclear weapons should serve defensive purposes.

Matsui said: "Leaders around the world must confront the reality that nuclear threats now being voiced by certain policymakers reveal the folly of nuclear deterrence theory. They must immediately take concrete steps to lead us from the dangerous present toward our ideal world."

Matsui also said Japan must immediately join the Treaty on the Prohibition of Nuclear Weapons. Nuclear powers like the US and Russia do not support the treaty. Japan and other countries which rely on them for deterrence have not signed it either.

Prime Minister Kishida Fumio said Japan is committed to pursuing a world without nuclear weapons, despite the challenges posed by the security environment.

Kishida said: "Today, the path towards our goal has become even harder, as the international community has become even more divided over how to advance nuclear disarmament and Russia threatens to use nuclear weapons. But it is all the more important, in the current situation, for us to rebuild international momentum towards a world without nuclear weapons."

Delegates from more than 100 countries attended this year's event.