Britain has issued an international arrest warrant for a second Russian man suspected over the murder of ex-agent turned dissident Alexander Litvinenko in London, the suspect and security sources said Thursday.

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, one of the last people to see Litvinenko in London before he fell ill, 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.

Kovtun -- a friend of Lugovoi and like him a former Russian secret service agent -- told the Moskovsky Komsomolets daily that the Crown Prosecution Service had asked for his extradition and said he was "extremely suprised".

"Interpol has been informed and if I appear somewhere in Europe then I will be arrested and sent to Britain as a suspect. Naturally, this does not please me at all."

But the Interfax source added that Russia had so far received "no approach from London about Kovtun and the spokesman for the Russian General Prosecutors said they had received no such request.

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.

But both Kovtun 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.

Lugovoi, who in the wake of the scandal became a deputy for the ultra-nationalist Liberal Democratic Party which gives him parliamentary immunity, said the targeting of Kovtun would arouse "indignation" in Russia.

He told Interfax there were signs in Britain of a "politicisation of the decision-making process and an attempt to take the process out of the realms of a real investigation."