Scotland Yard investigators arrived in the Russian capital Monday as part of their probe into the November 23 death of Alexander Litvinenko, a Russian security service defector. Britain had officially approached Russian authorities requesting cooperation in the case.
"The parties have outlined joint efforts, and expressed their willingness to maintain businesslike, constructive cooperation," - the office said.
In Moscow, British investigators were to interview several people who met with Litvinenko around the time of his alleged poisoning with radioactive polonium-210 in early November.
But they were not authorized to interview a jailed security officer who had sought a meeting with them, and who claims to have warned Litvinenko of a planned attempt on his life, to avenge his defection from the Russian security service.
Defense lawyers for Mikhail Trepashkin, in prison since 2004 for divulging state secrets, said Monday he was prepared to provide important evidence in the case to British investigators.
But a Federal Penitentiary Service spokesman, said: "Trepashkin is serving a sentence for treason, therefore we cannot allow him to contact foreign security services."
Litvinenko, 43 at the time of his death, had lived in London since 2000 and received citizenship in October 2006. His death has strained relations between Moscow and London.
The former agent purportedly left a deathbed message implicating President Vladimir Putin in his poisoning. Moscow has denied involvement, and also cast doubt over the authenticity of the note. Russian officials have condemned efforts to fan the scandal, saying they are willing to provide full assistance in the investigation.
