Amidst increased tensions between the U.S. and world powers including North Korea, the city of Hiroshima, Japan on Sunday marked the 72nd anniversary of the U.S. dropping of the atomic bomb with a call to rid the world of "the absolute evil that is nuclear weapons."

Hiroshima Mayor Kazumi Matsui, speaking to a crowd of roughly 50,000 people at the Peace Memorial Park, reiterated his calls for disarmament, as he described the sheer horror on Aug. 6 at 8:15am.

"This hell is not a thing of the past," he warned. "As long as nuclear weapons exist and policymakers threaten their use, their horror could leap into our present at any moment. You could find yourself suffering their cruelty."

Matsui's declaration elevated the calls from hibakusha—those who survived the atomic bombings—to "preserve our irreplaceable Earth for future generations," and it argued that "possessing nuclear weapons means nothing more than spending enormous sums of money to endanger all humanity."

This year's ceremony marking the event comes a month after the majority of the world's nations reached a historic nuclear weapons ban treaty. The nuclear-armed states, including the U.S. and North Korea, boycotted the treaty negotiations.

Matsui referenced the treaty's adoption, saying that with "this development, the governments of all countries must now strive to advance further toward a nuclear weapon-free world."

Though Prime Minister Shinzo Abe also spoke at the ceremony, he "avoided any mention of the" treaty, Kyodo reports. He later defended the decision not to take part in it. And at a news conference following the ceremony, the New York Times reports, when Abe was asked: "Should Japan, whose Constitution renounces war, acquire the means to strike North Korean missile sites if an attack on Japan appeared imminent?" he did not reject the idea outright. The Times reports:

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"At the present time, we are not planning any specific deliberations about possessing" weapons for a pre-emptive strike, Mr. Abe said. He added that Japan needed to strengthen its defenses generally, "given that the security situation surrounding Japan is becoming increasingly severe."

United Nations Secretary-General António Guterres's message to those gathered in Hiroshima acknowledged that the "dream of a world free of nuclear weapons remains far from reality," noting the existence of roughly 15,000 nuclear weapons. (The majority of those nuclear warheads are owned by the U.S. and Russia.)

Commenting on the anniversaries of Hiroshima and Nagasaki, where the U.S. dropped a second atomic bomb on Aug. 9, 1945, Paul Kawika Martin, senior director for policy and political affairs at Peace Action, warned of the increased nuclear threat.

"Last year, President Obama made a historic visit to Hiroshima and met with survivors. Will the Trump administration do more than spout bellicose threats of using nuclear weapons?” he asked.

Since Obama's visit to Hiroshima, Martin said, "tensions between the U.S. and North Korea are the highest they've been since the Korean War. Tensions between the U.S. and Russia are the highest they've been since the Cold War and friction with China continues. With these nuclear-armed adversaries each vying to improve their geopolitical positions and expand their nuclear capabilities, the need for dialogue and diplomacy to prevent conflict and support nonproliferation is readily apparent."

The International Campaign to Abolish Nuclear Weapons says that the Hiroshima and Nagaski bombings killed over 200,000 in 1945 and left a legacy of chronic disease still felt today.