Japan’s Prime Minister, Fumio Kishida, said on Saturday that the prospect of Russia using nuclear weapons was “increasingly real,” as he welcomed the visit of the US ambassador to Hiroshima, the first city to be hit by a nuclear blast.

Japan, the only country to have been attacked by nuclear weapons, has consistently spoken out against nuclear weapons. Kishida, who represents Hiroshima in parliament, and envoy Rahm Emanuel paid a visit to the city’s peace memorial and museum on Saturday.

“When the possible use of nuclear weapons by Russia is increasingly real, I believe Ambassador Emanuel’s visit to Hiroshima and his experience of seeing the nuclear reality will become a strong message to the international society,” Kishida told public broadcaster NHK.

“I believe our visit was meaningful.”

He said Russia’s war in Ukraine shows the difficulties of creating a world without nuclear weapons.

Putin has not directly threatened a nuclear attack. But he warned, in launching his Feb. 24 invasion, that anyone hindering Russia would face “such consequences that you have never encountered in your history” – a statement some leaders took as a threat to use nuclear weapons.

Kremlin spokesman Dmitry Peskov said on Tuesday that Russia would use nuclear weapons only to counter “an existential threat for our country”.

Leaders of the Group of Seven industrial powers on Thursday warned Russia not to use biological, chemical or nuclear weapons in its war with Ukraine.