The head of the Italian military intelligence service SISMI, Nicolo Pollari was questioned on Wednesday (July 19) by the country's Senate Defence Committee over the US's Central Intelligence Agency (CIA) kidnapping of a Muslim terrorist suspect. Pollari is the highest ranking official connected to the Italian investigation -- which had already led to the arrests of his No. 2, Marco Mancini, and another leader of his SISMI intelligence agency on July 5. Both were released from house arrest on Saturday (July 16) after repeated rounds of questioning. In his release order, Judge Paolo Ielo said their sworn statements had lent support to the investigation, according to a lawyer for one of the men. 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 while being questioned. A judicial source said prosecutors, investigating an Italian role in the abduction, questioned Pollari for about four hours at the Milan prosecutors' offices on July 15. The offices were were shut to the public and placed under heavy security. His appearance before the Senate Defence Commission was also held behind closed doors. Prime Minister Romano Prodi met U.S. President George W. Bush on Saturday in St. Petersburg but said the Nasr case did not come up. a report by a Council of Europe investigator last month said the case was one of the most disturbing in a "global spider's web" of secret CIA flights of terrorist suspects. Italy's former government and SISMI have denied a role, but investigator Dick Marty said it was unlikely that the Italian authorities were not aware of this "large-scale CIA operation." Pollari has not commented publicly on the issue so far. 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. Silvio Berlusconi, prime minister at the time of the abduction, has also denied any role and compared magistrates to "terrorists" for locking up intelligence agency officials meant to protect the country. Prodi's centre-left government has so far defended SISMI and Defence 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 investigation. The Egyptian cleric, now held in a prison outside 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 ($12,680) for its alleged role in his kidnap.