Alexander Litvinenko, who was living in London, died of poisoning by polonium 210 in 2006. Before his death, he blamed the government of Vladimir Putin.
Several cables released by WikiLeaks dealt with the question of who killed Litvinenko, The New York Times reported Tuesday. The cable including the claim the Russians had been tracking the killers was dated Dec. 26, 2006, about a month after his death.
British investigators say the polonium could have come from Russian stocks only with the assistance of senior officials.
"When they prepared this, they never expected polonium would be known as a murder weapon," Litvinkenko's widow, Marina, told the Times. "But after Nov. 23, they needed some kind of disinformation."
British agencies say the killing was carried out by Andrei Lugovoi, a former KGB agent who now sits in the Russian Parliament. Russian has refused his extradition.