Russian Spy Mystery

Dmitry Kovtun left traces of the radioactive substance which killed Litvinenko in a car, an office and his ex-wife's house in Hamburg before flying to London where he met with the former spy, the leader of the German investigation into the case, Thomas Menzel, said.

The German authorities have opened a criminal investigation against the businessman for bringing polonium into the country though they are not linking him directly to Litvinenko's killing.

"We found radiation in the car in which he drove after he arrived in Hamburg from Russia on October 28 and in a document he signed at the immigration offices," Menzel told reporters.

Investigators have also found traces of polonium 210 on the couch in Kovtun's ex-wife's flat where he slept on the night of Oct. 30, Menzel said.

"Tests have shown clearly that we are dealing with polonium 210," Gerald Kirchner from the Federal Office for Radiation Protection (BfS) told reporters, referring to the places visited by the businessman during his three-day stay in Germany.

Kovtun is one of three Russians who met with Kremlin critic Litvinenko in London on November 1, the day on which the former Russian spy fell ill. Kovtun has also been hospitalized with severe radioactive poisoning.

"He appeared to have been in active contact with polonium. We are considering him as a suspect also," Hamburg state prosecutor Martin Koehnke said. "We have to establish whether he was poisoned himself or carried the polonium into the country," Koehnke said.

He said German investigators would share all evidence they uncover with British counterparts probing the murder which friends and family of the victim have blamed squarely on the Russian government.

Litvinenko's widow blames "hit squad"

In her first public interviews since his death on Nov. 23, Litvinenko's widow Marina on Sunday stood by his death-bed accusation that he was killed by a Russian "hit squad" because of his openly critical views of the Kremlin.

"Obviously, it was not (Russian President Vladimir) Putin himself, of course not," the 44-year-old told the Mail on Sunday. "But what Putin does around him in Russia makes it possible to kill a British person on British soil. I believe that it could have been the Russian authorities."

Marina Litvinenko told the British press her husband immediately suspected he had been poisoned when he first fell ill on Nov. 1.

The former lieutenant-colonel in the Federal Security Services (FSB) who fell out with Moscow over the conflict in Chechnya died three weeks later after large quantities of polonium 210 were found in his body.

Litvinenko and his father Valter's accusations against Putin were supported Sunday by the former agent's friend, Vladimir Bukovsky, who told the BBC he was convinced of "clear" Russian involvement.

Moscow has launched its own probe, but associates of Litvinenko said they would only cooperate with Russian investigators if their safety were guaranteed.

A British Channel 4 television report this week quoted a senior British police source as saying that they believed Litvinenko was poisoned at the central London hotel where he met three Russian contacts on Nov. 1.

The probe widened to Germany after Hamburg police found that Kovtun was registered with the city's immigration authorities and found that he still owned a home there.