Italian magistrates on Wednesday interrogated Mario Scaramella, a self-styled expert on Soviet espionage who is under arrest in a case that centres on an alleged smear campaign against prime minister Romano Prodi.

Mr Scaramella, 36, caught the world's attention after it emerged that in a London sushi bar on November 1 he met Alexander Litvinenko, a former Russian spy who ingested a lethal dose of polonium that day.