Mario Scaramella, the Italian contact of the dead former Russian spy Alexander Litvinenko, was arrested today in connection with an investigation into arms trafficking, a judicial source said.
The source said Scaramella was arrested at Naples airport as he arrived on a flight from London, where he was hospitalised this month for treatment for suspected radiation poisoning.
He was one of the last people to have met with Litvinenko, who died last month of radiation poisoning.
Scaramella, an Italian KGB expert who was a consultant to an parliamentary commission that investigated spying in Europe during the Cold War, was arrested in connection with an investigation into arms trafficking and violating state secrets.
Italian media said he would be transferred to a Rome jail.
Scaramella met Litvinenko at a London sushi bar on Nov. 1, the day the former Russian spy fell ill.
Both Russian and British authorities have started murder investigations into Litvinenko's death from poisoning by a lethal dose of polonium 210.
The attention surrounding Scaramella has thrown the spotlight onto Italian judicial investigations that involve him, including one into arms trafficking.
In a telephone interview with Reuters earlier this month, Scaramella said: "I need to come back to Italy as soon as I can and to clarify with authorities," he said.
Litvinenko, in a statement released after his death on Nov. 23, accused Russian President Vladimir Putin of masterminding his poisoning.
The Kremlin has denied involvement in the case, which has sparked conspiracy theories, revived memories of Cold War spying and strained relations between Russia and Britain.
Marina Litvinenko, in media interviews, said her husband had made enemies by speaking out about corruption in the FSB, the KGB's successor. She said Russian authorities might have killed him.