The mayor called on the Japanese government to lead the global community towards "dialogue and cooperation for a world without nuclear weapons".
The number of people certified as hibakusha stood at 154,859 across the country at the end of March this year, according to the health ministry.
A cenotaph for A-bomb victims, center, and the Atomic Bomb Dome, bottom, are seen from a Mainichi Shimbun helicopter in Hiroshima's Naka Ward on August 6, 2018, as people attend a peace memorial ceremony.
In a speech during the ceremony, Abe said, "I'm determined to bridge nuclear and nonnuclear weapon states and lead worldwide efforts".
Participants in Monday's ceremony - survivors, Prime Minister Shinzo Abe and representatives from 80 countries - observed a minute's silence at 8:15 a.m., the moment when the United States dropped its payload on the unsuspecting population 73 years ago.
The 73rd anniversary comes after Pyongyang's promise of a complete denuclearization of the Korean Peninsula grabbed attention following the historic U.S.
Prime Minister Shinzo Abe says Japan is determined to lead efforts to bridge deepening rifts between countries that possess nuclear weapons and those that do not.
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Analysts still expect a less favorable overall trade balance for China in coming months given it's early days in the tariff brawl. China, on the other hand, argues that the tariffs violate World Trade Organization rules and only harm both countries.
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We have a good group, very homogeneous. "We feel good together and I hope that Lyon will have a very good season". Fekir posting his picture with Liverpool red background.
"We have to work on eliminating nuclear weapons", Tsuboi said at the meeting, held at a Hiroshima hotel. It was the first use of nuclear weapons against human beings.
The US attack on Hiroshima killed 140,000 people, and the bombing of Nagasaki killed more than 70,000 three days later, leading to Japan's surrender and ending World War II.
Over two years, the group of Japanese high school students has been painstakingly producing a five-minute virtual reality experience that recreates the sights and sounds of Hiroshima before, during and after the USA dropped an atomic bomb on the city 73 years ago.
In his speech at Hiroshima's Peace Memorial Park, Mayor Kazumi Matsui said certain nations were "rekindling tensions that had eased with the end of the Cold War", although he did not identify those nations. In order to gain cooperation from both sides, it is important for everyone to understand "the reality of the tragedy of nuclear attacks, " he said, and reiterated Japan's pledge to maintain it pacifist and non-nuclear principles. "I never heard the words 'atomic bomb, '" he told NPR.
Atomic bomb survivors and many visitors prayed for peace at the Peace Memorial Park near Ground Zero under the scorching summer heat.
This computer graphic image provided by Fukuyama Technical High School shows a burning building just after an atomic bomb fell in Hiroshima, western Japan.
The Hiroshima mayor regarded the nuclear weapons ban treaty as "a milestone along the path to a nuclear-weapon-free world", urging the government of Japan to play a role to help bring it into force.