Marking the 73rd anniversary of the U.S. atomic bomb attack, Hiroshima once again fell silent Monday morning while traffic came to a halt in remembrance of those lost, with dignitaries urging world leaders to strengthen efforts to abandon nuclear weapons and highlighting the slow progress toward abolition.

In the city's annual Peace Declaration, Hiroshima Mayor Kazumi Matsui urged world leaders to make the landmark U.N. treaty prohibiting nuclear weapons "a milestone along the path to a nuclear-weapon-free world," but stopped short of calling on Tokyo to join the 2017 pact.

The mayor also touched on the rise of self-centered nationalism around the world, alluding to the administration of U.S. President Donald Trump and warning that with 14,000 nuclear warheads remaining worldwide, "the likelihood is growing that what we saw in Hiroshima after the explosion will return, by intent or accident, plunging people into agony."