Two Italian spy chiefs were arrested on Wednesday and a judge issued arrest warrants for four Americans over the alleged CIA kidnapping of a terrorism suspect in Milan in 2003, officials said.
Three of the Americans were alleged CIA agents and the fourth worked at a US military base in Aviano, northern Italy, which prosecutors believe was used to secretly transfer the Muslim cleric out of Italy.
A statement from the Milan prosecutor's office said police arrested Marco Mancini, the No 2 at Italy's Sismi military intelligence agency, and were holding him in jail for his alleged role in the kidnap. Another Sismi official was placed under house arrest.
The police sweep ties all the suspects to the 2003 abduction of Hassan Mustafa Osama Nasr, also known as Abu Omar. Prosecutors say he was seized by a CIA-led team on a Milan street in broad daylight, bundled into a van and driven to the Aviano air base. He was then flown to Egypt and, according to Nasr, tortured under questioning.
An Italian court has already issued arrest warrants for 22 suspected US agents over the abduction. But it was the first time Italian officials have been linked to the investigation. If an Italian role is confirmed, it would lend evidence to allegations that European countries colluded with Washington in the secret "renditions", or transfers, of terrorism suspects.
Lawmakers in Italy's new centre-left ruling coalition accused former Prime Minister Silvio Berlusconi of a cover-up during his five-year administration, which ended in April.
Berlusconi, a close ally of President George W. Bush, has fiercely denied that his government or Sismi were involved in the kidnapping - and even once summoned the US ambassador over the matter to request Italian sovereignty be respected.