The Russian state backed the murder in London of former KGB agent and Kremlin critic Alexander Litvinenko, according to British security sources quoted by the BBC on Monday.
A senior security official, cited by BBC TV's Newsnight, said there were "very strong indications it was a state action".
The accusations come on the day that British Prime Minister Gordon Brown met Russian President Dmitry Medvedev for the first time since Medvedev took office in May.
Their talks at the summit of G8 leaders in Japan were an attempt to ease tensions created since 2006 by the Litvinenko affair.
Moscow and London established cordial ties after Medvedev's predecessor Vladimir Putin came to power in 2000. But they soured when Russia accused Britain of hosting the Kremlin's political foes -- self-exiled businessman Boris Berezovsky and Chechen rebel leader Akhmed Zakayev.
Relations between the two countries reached their lowest point since the Cold War after Russia refused to extradite to Britain ex-security guard Andrei Lugovoy, accused of poisoning Litvinenko in London almost two years ago.
Russia strongly denies state involvement in the killing. It refuses to hand over Lugovoy because its constitution bars it from extraditing its own nationals. The BBC said it had been told Russia's security service, the FSB, operated under Putin with far more autonomy than organisations usually entrusted with foreign espionage operations.
"We very strongly believe the Litvinenko case to have some state involvement," the source said.
Newsnight said the British Secret Service also believed it thwarted an attempt last year to kill Berezovsky.
That alleged attempt, the source said, showed "continued FSB willingness to consider operations against people in the West".
Last Mod: 08 Temmuz 2008, 14:19