Ukrainian President Volodymyr Zelenskyy has hailed his participation in the Group of Seven summit in Hiroshima over the weekend a diplomatic success, saying he has earned the understanding of many countries as Russia's war against his country rages.

Ukrainian President Volodymyr Zelenskyy signs a guest book at the Hiroshima Peace Memorial Museum on May 21, 2023. (Kyodo)

"We have an understanding with the world majority on every important point for Ukraine," including the return of all Ukrainian territories held by Russia and security guarantees, Zelenskyy said in a video message addressed to the Ukrainian people after wrapping up his two-day visit to Japan through Sunday.

"The world hears our position," he said in the video taken from inside a plane.

When he visited the Hiroshima Peace Memorial Museum on Sunday, he wrote in a guest book, "The threat of the use of nuclear weapons has no place in the modern world."

His entry, written in Ukrainian, was made public Monday by the Japanese Foreign Ministry and came amid concerns that Russia may use a nuclear weapon in its ongoing war against Ukraine.

Zelenskyy also wrote in the guest book, "No country in the world should experience such pain and destruction," and that he was "deeply moved" by his visit to the museum.

His visit to the museum, which exhibits the destruction wrought by the U.S. atomic bombing on the western Japan city in 1945, lasted around 40 minutes. He also met with Keiko Ogura, 85, who told him about her experience as an atomic bomb victim.

Together with Japanese Prime Minister Fumio Kishida, Zelenskyy laid flowers at a cenotaph dedicated to the victims and inscribed with a vow never to repeat the tragedy.

He also held separate talks with Kishida, U.S. President Joe Biden, Indian Prime Minister Narendra Modi and other leaders on the sidelines of the summit.

Before heading to Asia, the Ukrainian president had attended the Arab League meeting in Jeddah, Saudi Arabia.

On Sunday, via the encrypted messaging app Telegram, Zelenskyy thanked Hiroshima, Kishida and the Japanese people for their "comprehensive support."