Britain's senior law enforcement official said Sunday an inquiry into the death of a former KGB agent had expanded overseas, and a U.S.-based friend of the former agent said he told police the name of the person he believes orchestrated the poisoning.
The friend, Yuri Shvets, said he had known Alexander Litvinenko since 2002 and spoke with him on Nov. 23, the day Litvinenko died following his exposure to a rare radioactive element, polonium-210.
"The truth is, we have an act of international terrorism on our hands. I happen to believe I know who is behind the death of my friend Sasha and the reason for his murder," Shvets said, referring to Litvinenko by his Russian nickname.
Shvets, also a former KGB officer, declined to confirm the name of the person he believed was behind Litvinenko's death because of concern it could disrupt the investigation. He also declined to offer details on a document he said he had given to police.
Shvets said he was questioned by Scotland Yard officers and an FBI agent in Washington last week. A police official in London, speaking to the Associated Press on condition of anonymity, confirmed officers had interviewed Shvets.
Shvets, who has worked at the Center for Counterintelligence and Security Studies in Washington, would not confirm his precise location because of concern for his personal security.
British Home Secretary John Reid said the inquiry would go wherever "the police take it."
"Over the next few days I think all of these things I think will widen out a little from the circle just being here in Britain," Reid told Britain's Sky News television.
The British police official said police were expected to travel to Russia to interview a number of people, including Andrei Lugovoi. He is another former Russian spy who met with Litvinenko on Nov. 1, the day Litvinenko fell ill.
The Sunday Times newspaper quoted Lugovoi as saying he had also been contaminated with polonium-210, but he did not say whether he had fallen ill.
Litvinenko said he believed Russian President Vladimir Putin was behind his poisoning. Putin has dismissed the accusation as "nonsense."
Another person who met with Litvinenko on Nov. 1, the Italian security consultant Mario Scaramella, has said he gave Litvinenko an e-mail he had received naming the purported killers of Russian journalist Anna Politkovskaya, who was gunned down Oct. 7 in Moscow. The e-mail reportedly said that Scaramella and Litvinenko - a friend of the reporter - were also on the hit list.