A newspaper has reported that British anti-terror police have thwarted a plot to kill Russian President Vladimir Putin and arrested two would-be assassins.
The source said two men had been arrested in connection with the claims but had been released without charge and had returned to Russia as scheduled.
The Sunday Timesnewspaper said the men, one allegedly a former Russian secret service hit man, were hatching a plot for Putin to be shot by a sniper while on a foreign trip.
It said the former Russian agent knew a senior officer in the Federal Security Service (FSB), Russia's state security service and successor to the Soviet KGB, who would provide information about Putin's movements while abroad, allowing assassins to set up a hit.
Details had been given to British police by Alexander Litvinenko, a former FSB officer who defected to Britain three years ago, after he had been contacted by the alleged plotter, the newspaper said.
Police confirmed two men, aged 40 and 36, were held by police last Sunday in connection with the allegation but they were released on Friday after questioning and said no further action would be taken against them.
"If Scotland Yard gets an allegation of this kind it has to investigate if there's any truth in it. It seems like there wasn't in this case," a police source told Reuters.
When Litvinenko defected to Britain, his lawyer said the former spy had made allegations, denied by the FSB, that the Russian security services had planned to assassinate prominent Russian businessman Boris Berezovsky, who became a media mogul under President Boris Yeltsin but then fell out with Putin.
Berezovsky, granted political asylum in Britain last month, also recently claimed that Russian agents were plotting to kill him in London.