South Korean President Yoon Suk Yeol and Japanese Prime Minister Fumio Kishida together laid flowers at a memorial for Korean atomic bomb victims in Hiroshima, in a display of the warming ties that have helped cooperation with their mutual US ally.

Dressed in somber colors, the two leaders and their wives bowed silently at the monument Sunday after laying bouquets of white flowers. The brief ceremony took place on the sidelines of the Group of Seven summit in Hiroshima, where 78 years ago the world’s first atomic strike killed an estimated 140,000 people including Koreans.

Yoon praised Kishida’s “courage and resolve” in becoming the first Japanese premier to pay respects at the monument jointly with his South Korean counterpart.

“This is extremely important not only for relations between South Korea and Japan, but to pray for global peace,” Kishida said, as the two held bilateral talks after the visit. It was their third summit in about the span of two months as the two resumed shuttle diplomacy that had been suspended for about a dozen years due to political acrimony.

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The 1945 atomic blast took place during Japan’s 1910-1945 colonial rule over the Korean Peninsula. Disagreements over compensation for Koreans conscripted to work at Japanese factories and mines during that period had turned relations their coldest in decades.

Yoon has taken steps to try to resolve the issues so that the two can work more closely with the US to stave off threats from North Korea. The joint visit is seen as a show of willingness by Kishida to acknowledge Japan’s colonial past, as well as draw attention to the horrors of nuclear war.

Earlier in the week, Yoon became the first South Korean president to formally meet Korean survivors of the bomb. Kishida, who has family roots in Hiroshima, used his role as summit host to press for the revival of international momentum toward nuclear disarmament, as Russia escalates atomic threats in its war against Ukraine, while China also builds its arsenal. The leaders issued a statement calling for progress on disarmament on Friday.

The friction between Seoul and Tokyo, which threatened military and trade ties, caused headaches for the US. The Biden administration has been seeking help from its partners to impose sweeping curbs on the sale of advanced chip equipment to China in a policy aimed at hampering the country’s progression in a range of cutting-edge technologies.

--With assistance from Heejin Kim.