The deputy chairman of Russia’s Security Council was reacting to remarks by British defence secretary Grant Shapps who on Saturday said London wants to send military instructors to Ukraine – a claim later clarified by prime minister Rishi Sunak who said that the plans are not for “here and now”.
"(This will) turn their instructors into a legal target for our armed forces... understanding perfectly well that they will be ruthlessly destroyed. And not as mercenaries, but namely as British Nato specialists," Mr Medvedev wrote on his official Telegram channel.
Mr Shapps spoke about the training in Ukraine in addition to training Ukrainian armed forces in Britain or other Western countries as at present.
The Russian official is considered to be a close aide of Vladimir Putin who has earlier issued nuclear sabre-rattling threats after Russia launched a full-scale invasion of Ukraine in February last year.
Apart from threatening British forces in his Telegram post, Mr Medvedev also said German factories producing Taurus missiles were “pushing us towards World War Three”.
"They say this is in accordance with international law. Well, in that case, strikes on German factories where these missiles are made would also be in full compliance with international law," Mr Medvedev said.
"These morons are actively pushing us towards World War Three," he added, repeating similar warnings he has made before. In July, Mr Medvedev said actions by the "completely crazy" West meant World War Three "is getting closer."
On Sunday, Mr Sunak rowed back from his defence secretary Mr Shapps’s comments and said there were no immediate plans to deploy military instructors to Ukraine.
"What the defence secretary was saying was that it might well be possible one day in the future for us to do some of that training in Ukraine," he told reporters at the start of the governing Conservative Party’s annual conference in Manchester.
"But that’s something for the long term, not the here and now. There are no British soldiers that will be sent to fight in the current conflict."