The head of Italy's military intelligence agency was questioned by prosecutors for the first time on Saturday on suspicion of helping the CIA kidnap a terrorism suspect in Milan, judicial sources said.

The development makes Nicolo Pollari the highest ranking official connected to the Italian investigation -- which has already led to the arrests of his No. 2 and another leader of his Sismi intelligence agency earlier this month.

Twenty-six Americans, most believed to be CIA agents, face arrest warrants over the 2003 abduction of radical Muslim cleric Hassan Mustafa Osama Nasr, also known as Abu Omar.

Prosecutors say a CIA-led team grabbed Nasr off a Milan street, bundled him into a van and flew him to his native Egypt. Nasr says he was tortured there under questioning.

A judicial source said prosecutors, investigating an Italian role in the abduction, questioned Pollari for about four hours at the Milan prosecutors' offices, which were shut to the public and placed under heavy security.

A report by a Council of Europe investigator last month identified the case as one of the most disturbing in an alleged "global spider's web" of secret CIA flights of terrorist suspects.

Although Italy's former centre-right government and Sismi have denied any role, investigator Dick Marty said: "It is unlikely that the Italian authorities were not aware of this large-scale CIA operation."

Pollari could not be reached for comment. He has said Sismi had no knowledge of a plot to kidnap Nasr, who had political refugee status in Italy at the time of his abduction.

Former Prime Minister Silvio Berlusconi, who was in power at the time of the abduction, has also denied any role and compared magistrates to "terrorists" for locking up the intelligence agency officials meant to protect the country.

The centre-left government has so far defended Sismi and Defense Minister Arturo Parisi has encouraged Italians to distinguish between the agency and possible wrongdoing by some of its spies -- an argument that becomes increasingly difficult with its top officials under the investigation.

The Egyptian cleric, who is being held in a prison outside of Cairo, faces an Italian arrest warrant for suspicion of terrorist activity including recruiting militants for Iraq.

He plans to sue Italy for 10,000 euros for its alleged role in the kidnap.

PHOTO CAPTION

Italy's secret service chief Nicolo Pollari lis shown in this November 3, 2005 photo. (Tony Gentile. (Reuters)