A key witness in the radiation death of former Russian security agent Alexander Litvinenko claimed the poisoning took place earlier than is widely believed, a newspaper reported Wednesday.

Andrei Lugovoi, a security agent-turned-businessman who met with Litvinenko at a London hotel on Nov. 1, the day Litvinenko suspected he was poisoned, said in an interview with the Moskovsky Komsomolets tabloid that he and Litvinenko were poisoned on Oct. 16.

"Who told you that the contamination took place on Nov. 1? It took place much earlier, on Oct. 16," Lugovoi was quoted as saying by the paper. Lugovoi is himself undergoing radiation checks in a Moscow clinic.

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Litvinenko, 43, a former Russian agent and a Kremlin critic, died Nov. 23 of poisoning from polonium-210.

Lugovoi supported his claim by saying that he and Litvinenko visited a London-based security firm where traces of polonium were later found only in mid-October, but did not go there on Nov. 1, meaning that the contamination couldn't have taken place on that day.

Lugovoi's comments echo those made by another associate of Litvinenko, Russian businessman Dmitry Kovtun, who claimed in an interview with Germany's Spiegel TV that he must have been contaminated during meetings with Litvinenko and Lugovoi in London in mid-October.

Both Lugovoi and Kovtun, have been questioned in Moscow by visiting Scotland Yard investigators and have denied involvement in Litvinenko's poisoning. The Russian Prosecutor General's office says Kovtun has been diagnosed with radiation poisoning. He is reportedly being treated in Russia.

Meanwhile, German investigators are also probing Kovtun on suspicion that he may have illegally handled radioactive material. German authorities have found traces of polonium-210 in locations visited by Kovtun before he traveled to London on Nov. 1.

They say Kovtun flew to Hamburg from Moscow on Oct. 28 and departed for London on Nov. 1. Traces of polonium-210 have been confirmed in the passenger seat of the BMW car that picked up Kovtun from the Hamburg airport.

That makes German officials believe that Kovtun already was contaminated with polonium-210 when he arrived in Hamburg — but how that happened is unclear.

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