Japanese Prime Minister Fumio Kishida says the use of a nuclear weapon by Russia in the war in Ukraine would be considered an "act of hostility against humanity."
"Russia's act of threatening the use of nuclear weapons is a serious threat to the peace and security of the international community and absolutely unacceptable," Kishida said on October 22 during a visit to Australia.
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In May next year, Kishida is expected to host leaders from the Group of Seven (G7) leading industrialized nations in Hiroshima, where a U.S. nuclear bomb was dropped on August 6, 1945, resulting in the deaths of 140,000 people.
The Japanese city of Nagasaki was hit three days later.
Japan remains the only country to have ever been hit with a nuclear bomb.
Kishida said the 77-year period of no nuclear weapons use "must not be ended."
"If nuclear weapons were ever used, that would be an act of hostility against humanity...the international community will never allow such an act," he said, adding that President Vladimir Putin's nuclear allusions are "deeply disturbing."
Putin has made several thinly veiled threats about his willingness to deploy tactical nuclear weapons against Ukraine.