Vladimir Putin told French president Emmanuel Macron that the nuclear attacks on Hiroshima and Nagasaki show “you don’t need to attack major cities in order to end a war,” according to reports.
The threat of a Russian atomic strike – particularly one with tactical nuclear weapons which are designed to cause devastation on the battlefield – has been speculated on at the highest level by Ukraine and Western allies.
Reports in the US media said Washington had intelligence showing that senior Russian officials had recently held conversations to discuss when and how Moscow might use a tactical nuclear weapon in Ukraine.
But many in the West doubt the Russian president would risk the global backlash that would follow the crossing of so firm a red line.
This week, former British prime minister Boris Johnson said he did not believe Mr Putin would order use of a tactical nuclear weapon, saying the act would “immediately tender Russia’s resignation from the club of civilized nations”.
Russia has been warned by allies against any such strike. Chinese president Xi Jinping on Friday condemned the Kremlin’s nuclear threats.
Moscow denies having plans to draw on its vast nuclear arsenal – despite repeated hints to the contrary by Mr Putin – and has repeatedly made an unevidenced claim that Ukraine intends to use a radioactive “dirty bomb”.
The Mail on Sunday reported a French government source as saying the Russian president referenced Hiroshima in a call with Mr. Macron which left the French president “distinctly alarmed”.
“It sounded like a very heavy hint that Putin might detonate a tactical nuclear weapon in the east of Ukraine, while leaving Kyiv intact,” the source said. “That appeared to be the thrust of his remarks.”
“The two presidents have undoubtedly discussed the risk of nuclear weapons use. Putin wants to get the message across that all options are on the table, in line with Russian doctrine relating to nuclear weapons.”
The date of the call was not given. Mr. Macron has spoken to Mr. Putin several times during the war.
In September, Mr Putin issued his clearest threat that he was willing to use nuclear weapons, saying “all means” would be employed to defend Russia’s territory.
He also claimed the US had created a precedent at the end of the Second World War when it dropped atomic bombs on Japan.
A survivor of the bombing of Hiroshima on 6 August 1945 last week said he thought the world could soon see another nuclear attack.