Russia has engaged in an unusual burst of contact with the West’s three nuclear powers to raise baseless claims about a dirty bomb plot in Ukraine, amid fears of further escalation.

In the past 48 hours, Vladimir Putin’s defence minister, Sergei Shoigu, has spoken to his respective counterparts in the US, the UK and France, while the Russian president’s top military chief, General Valery Gerasimov, has separately spoken to his US and UK counterparts.

Russia used the conversations, which it initiated, to claim that Ukraine is preparing to deploy a ‘dirty bomb’ on its own territory – an allegation strongly rejected by the allies. A dirty bomb is an explosive device laced with radioactive material.

The West has long suspected Moscow of being ready to carry out a major ‘false flag’ operation – launching an attack but blaming the Ukrainians and then using the carnage as a pretext for a further escalation by the Russian side.

The sudden desire for dialogue could be part of the process of raising the idea of a dirty bomb ahead of whatever theatrics could be planned.

At the same time, it could possibly signal that Moscow is trying to attempt some form of renewed contact, or even negotiation, as its armed forces suffer repeated defeats on the battlefield at the hands of Ukraine’s military, armed with Western weapons, and with winter approaching.

Jens Stoltenberg, the head of the NATO alliance, said on Monday that he had spoken to Lloyd Austin, the US defence secretary, and Ben Wallace of the UK about “Russia’s false claim that Ukraine is preparing to use a dirty bomb”.

More on Nato

“NATO allies reject this allegation,” Mr Stoltenberg said in a statement on Twitter. “Russia must not use it as a pretext for escalation. We must remain steadfast in our support for Ukraine.”

Washington, London and Paris also released a rare joint statement about the contact with Russia, reiterating their “steadfast support” for Ukraine and flagging the discussions on Sunday between Russian defence minister Sergei Shoigu and Mr Austin, Mr Wallace and Sebastien Lecornu of France.

Please use Chrome browser for a more accessible video player


John Sparks joins Ukrainian soldiers fighting around the strategically important town of Bakhmut in eastern Ukraine

What is a dirty bomb?

“Our countries made clear that we all reject Russia’s transparently false allegations that Ukraine is preparing to use a dirty bomb on its own territory,” the statement said.

“The world would see through any attempt to use this allegation as a pretext for escalation. We further reject any pretext for escalation by Russia.”

On Monday – a day after the talks with defence ministers – Russia’s General Gerasimov spoke to General Mark Milley, the top military officer in the US, and had a separate conversation with Admiral Sir Tony Radakin, the UK’s chief of the defence staff.

The UK Ministry of Defence said Admiral Radakin “rejected Russia’s allegations that Ukraine is planning actions to escalate the conflict, and he restated the UK’s enduring support for Ukraine”.

It added: “The military leaders both agreed on the importance of maintaining open channels of communication between the UK and Russia to manage the risk of miscalculation and to facilitate de-escalation.”