Vladimir Putin put Russia’s nuclear forces on high alert after comments by UK Foreign Secretary Liz Truss and others, the Kremlin has said.

Kremlin spokesman Dmitry Peskov said “unacceptable” remarks were made about possible “clashes” between Nato and Moscow over Russia’s attack on Ukraine.

It is unclear precisely which comments by Ms Truss Russia objects to.

On Sunday, she said if Russia was not stopped, other states may be threatened and it could end in conflict with Nato.

A Foreign and Commonwealth Office source told the BBC: “I don’t think anything Liz has said warrants that sort of rhetoric or escalation.”

They said the foreign secretary had always spoken about Nato as a “defensive alliance” and that the UK needed to support Ukraine.

Echoing comments by Defense Secretary Ben Wallace earlier, the source insisted the UK wanted to avoid “any sort of miscalculation”.

Speaking at a press briefing on Monday, Mr Peskov said: “Statements were made by various representatives at various levels on possible altercations or even collisions and clashes between Nato and Russia.

“We believe that such statements are absolutely unacceptable. I would not call the authors of these statements by name, although it was the British foreign minister.”

Speaking to Sky News’s Trevor Phillips on Sunday, Ms Truss warned that if the Russian president was not stopped in Ukraine, there could be “conflict” between Russia and Nato.

“This long-running conflict is about freedom and democracy in Europe,” she said.

“If we don’t stop Putin in Ukraine, we are going to see others under threat: the Baltics, Poland, Moldova, and it could end up in a conflict with Nato. We do not want to go there.”