Britain has issued an international arrest warrant for a new Russian suspect in the murder of ex-agent turned dissident Alexander Litvinenko in London, the Interfax news agency quoted a security source as saying.
Britain has already demanded the extradition from Russia of former agent Andrei Lugovoi on suspicion of murdering Litvinenko in London 2006, a request snubbed by Moscow in a row that has severely hurt relations with London.
Britain has now issued an order for the arrest of businessman Dmitry Kovtun, who had previously been linked to the case as he had met Litvinenko in London, the Interfax news agency quoted a Russian security source as saying.
"On the basis of the warrant, the Russian citizen should be arrested by the authorities in the country where he is currently located," the source said.
But the source added that Russia had so far received "no approach from London about Kovtun".
Litvinenko, 43, a former officer for the FSB Russian security service turned Kremlin critic, died in hospital after drinking tea laced with polonium at a London hotel in November 2006.
Kovtun earlier this week told the Russian service of the BBC that Russian officials had informed him that British prosecutors had asked Russia for his extradition.
"Russia's position is absolutely clear on this and I hope that it is set in stone," he said, referring to the refusal of Moscow to extradite suspects. "The accusation is completely absurd."
Kovtun, a friend of Lugovoi and like him also a former secret service agent, was one of the last people to see Litvinenko in London before he fell ill.
But both he and Lugovoi have always said that rather than being behind the plot, they were themselves victims of the radiation and underwent treatment.
Russia's investigative committee announced last year that it now considered both the Russians to be victims of attempted murder and that it was investigating this crime as a single case with the Litvinenko murder.