It was on August 6 and 9 in 1945 that America had dropped bombs on Hiroshima and Nagasaki respectively.
The U.N. estimates nations around the world still have some 15,000 nuclear weapons in their arsenals.
Sunday marks a somber anniversary - the day the US dropped the atomic bomb on Hiroshima, Japan on August 6, 1945, 72 years ago.
On a positive note, he highlighted a major development in 2017, in particular the adoption last month of the treaty on the prohibition of nuclear weapons by UN Member States.
Japan is the only country to have suffered atomic attacks.
Graphically depicting the horror of atom bomb, along with NSS volunteers of SNDT University and University of Mumbai, school students, social activists and peace-loving citizens in the city marched for peace and a nuclear-free world.
Trump defends McMaster as conservatives seek his dismissal
Kelly has also sought to tamp down on the type of death-by-leak that now is plaguing his former military colleague. The crisis is linked to McMaster's decision to remove four Bannon allies from the National Security Council .
"This hell is not a thing of the past", Hiroshima Mayor Kazumi Matsui said at the ceremony. This has brought deep unease in Hiroshima, even as many Japanese appear resigned to the growing threat. You could find yourself suffering their cruelty.
He referred to the adoption in July 2017 of the treaty on the prohibition of nuclear weapons by United Nations member states as a positive development.
He referred to the Treaty on the Prohibition of Nuclear Weapons approved July 7 at a United Nations conference and said, "the governments of all countries must now strive to advance further toward a nuclear-weapon-free world".
None of the nine countries that possess nuclear weapons took part in the negotiations or voted on the treaty.
Many in Japan feel the attacks on Hiroshima and Nagasaki amounted to war crimes and atrocities because they targeted civilians, and also because of the unprecedented destructive nature of the weapons.