MOSCOW, July 8 (RIA Novosti) - Russia's top investigators said on Tuesday they have made substantial progress in investigating the 2006 killing of a Russian security service defector in London, and rejected claims of the Kremlin's role in his death.

The latest claims emerged in a BBC program aired on Monday, which quoted a senior British security official as saying there were "very strong indications" the killing was a "state action" by Russia.

The report came on the day of Russian President Dmitry Medvedev's first meeting with British Prime Minister Gordon Brown, at the Group of Eight summit in Japan.

Vladimir Markin, a spokesman for the Investigations Committee of the Prosecutor General's Office, told RIA Novosti: "Investigators have made significant progress, but have no evidence that any special service was involved in the crime."

Alexander Litvinenko died of radioactive poisoning in London in on November 23, 2006, three weeks after suddenly falling ill. British investigators accused Russian agent-turned-businessman Andrei Lugovoi over the murder, and demanded his extradition, sparking a major diplomatic row with Moscow.

Russian presidential aide Sergei Prikhodko said the timing of the British report was no coincidence, and was aimed at scuppering efforts to mend ties between the countries, the main theme of the leaders' discussions on Monday.

"We are trying to work to bring Russian-British relations out of this dead-end. These various leaks and rumors show that unfortunately in Britain not everyone shares the constructive frame of mind that we have sensed from the prime minister," he said.