Boris Johnson said Putin threatened the UK with a missile strike before it invaded Ukraine.
The then-prime minister said he was trying to convince Putin not to invade.
He said Putin told him: "I don't want to hurt you but, with a missile, it would only take a minute."
The UK's former prime minister said that President Vladimir Putin of Russia threatened his country with a missile attack during a February 2022 phone call, just weeks before the start of Russia's invasion of Ukraine.
Boris Johnson, who was the UK prime minister when Russia invaded Ukraine later in February 2022, told the BBC that he had a phone call with Putin in the run-up to the invasion, where he tried to persuade Putin not to go ahead with the attack.
"He threatened me at one point, and said: 'Boris, I don't want to hurt you but, with a missile, it would only take a minute' or something like that," Johnson said, recalling the conversation.
Johnson said Putin was talking in a relaxed and detached manner.
"I think from the very relaxed tone that he was taking, the sort of air of detachment that he seemed to have, he was just playing along with my attempts to get him to negotiate," he said.
Johnson described it as the "most extraordinary call" in an interview for a new BBC documentary.
He added that he told Putin that war would be a "utter catastrophe" and that Russia's apparent fear that Ukraine would join the NATO military alliance would not come true "for the foreseeable future."
He also told Putin that invading Ukraine would result in sanctions from the West and more NATO troops stationed along Russia's borders, according to his recollection.
Both of those predictions came true.
A Kremlin spokesman denied the comments, calling them either a "deliberate falsehood" or a misunderstanding on the part of Johnson.
"There were no threats to use missiles," Dmitry Peskov told the BBC.
Johnson was seen as one of Ukraine's biggest allies following the Russian invasion, and has made multiple trips to the country, both during his time as prime minister and after.
While it is impossible to know if Putin's perceived threat was genuine, the BBC pointed to Russia's previous meddling in the UK, including the 2018 poisoning of a former Russian agent and his daughter in the city of Salisbury, for which three Russian nationals were charged.