Japan on Saturday marked the 71st anniversary of the U.S. nuclear bombing of Hiroshima that led to the end of World War Two.
About 50,000 people attended a ceremony at Hiroshima's Peace Park near the bomb's epicenter.
Mayor Kazumi Matsui called on world leaders to visit the site, like U.S. President Barack Obama did in May.
Like Obama, Matsui said that such visits "will surely etch the reality of the atomic bombings in each heart."
The Hiroshima bombing killed around 140,000 people either instantly or from radiation burns in the immediate aftermath.
Another bomb was dropped on the port city of Nagasaki three days later, killing an estimated 70,000 residents.
Washington argued the attacks were necessary to bring about a quicker end to the war. Six days after the Nagasaki attack, Japan surrendered, ending the war.
When he visited the site, Obama said, "We have a shared responsibility to look directly in the eye of history. We must ask what we must do differently to curb such suffering again. We must re-imagine our connection to one another as members of the human race."
Obama is the first sitting U.S. president to visit the bomb site. He did not offer an apology for the bombing. He had said he would not revisit then president Harry Truman's decision.