During World War II, an American B-29 bomber called the ‘Enola Gay’ dropped an atomic bomb over Hiroshima, Japan, on the morning of Aug. 6, 1945. The bomb killed close to 80,000 people instantly and the death toll later went up to about 135,000. Several died of the long-term effects of radiation sickness.

It was the first time — and one of the only two instances — that an atom bomb was used in warfare, and it precipitated the end of the war in Asia.

On Saturday, 71 years after the bombing, at least 50,000 people attended a memorial ceremony at Hiroshima’s Peace Park where Japanese officials urged world leaders to visit bombing sites and to actively fight for a world devoid of nuclear weapons. In an annual speech — called the Peace Declaration — on the anniversary of the bombing, Hiroshima Mayor Kazumi Matsui quoted an excerpt from U.S. President Barack Obama’s speech which he delivered at the same venue during a visit in May.

Obama Hiroshima message An entry message written by U.S. President Barack Obama is seen on a guestbook after he visited Hiroshima Peace Memorial Museum, which displays various artifacts and items belonging to victims of the 1945 U.S. atomic bombing, in Hiroshima, Japan, May 27, 2016. Photo: KYODO/VIA REUTERS

“Those nations like my own that hold nuclear stockpiles, we must have the courage to escape the logic of fear, and pursue a world without them,” Obama said. He was the first sitting U.S. president to visit Hiroshima.

Matsui added that Obama’s words showed that he was touched by the “spirit of Hiroshima.” He also said that leaders visiting bombing sites “will surely etch the reality of the atomic bombings in each heart.”

“We need to fill our policymakers with the passion to solidify this unity and create a security system based on trust and dialogue,” the mayor reportedly said, “To that end, I once again urge the leaders of all nations to visit the A-bombed cities.”

He called for a partnership between Japanese Prime Minister Shinzo Abe and Obama in ridding the world of nuclear weapons. “A nuclear weapon-free world would manifest the noble pacifism of the Japanese Constitution,” he said.

Hiroshima 71st anniversary A mother tends her injured child, a victim of the 1945 atomic bomb blast at Hiroshima, Japan. Photo: KEYSTONE/GETTY IMAGES

Abe, in his address during the ceremony, said that Japan, the only country that suffered due to atomic bombings,  will continue to stick to its non-nuclear principles and will help maintain and promote the Nuclear Non-Proliferation Treaty which prevents member countries from pursuing atomic weapons programs.

Representatives from 91 countries — including countries that possess nuclear weapons, like Britain, France, Russia and the U.S. — attended the ceremony. Representatives from the European Union and the United Nations were also present.