Mohammed Haydar al-Zammar, 45, a Syrian-born German national, was "sentenced to death for membership of the Muslim Brotherhood but the sentence was commuted to 12 years imprisonment," the National Organization for Human Rights in Syria said.

Membership of the opposition Muslim Brotherhood has been outlawed on pain of death in Syria since 1980 although for the past decade courts have always commuted the mandatory death sentence.

Syria's state security court operates under the four-decade-old state of emergency and its verdicts cannot be appealed.

Supporters claim sentence has an alterior motive

"This is a grossly unjust verdict," human rights activist Ammar al-Qurabi told reporters after the verdict. "They could not prove a link between Zammar and the September attacks so they sentenced him for belonging to the Muslim Brotherhood when he was not wanted by Syria for belonging to the group in the first place," Qurabi said.

Zammar's lawyer Mohanad al-Husni told Reuters his client had always maintained his innocence. "This religious man had the misfortune of frequenting the same mosques in Hamburg as al Qaeda members. He kept telling the judge he had no organizational links with any Muslim group," Husni said.

Zammar was handed over to Syrian custody in December 2001, just two weeks after his arrest in Morocco. His trial opened last October.

He was briefly detained in Germany in October 2001 as he was suspected of having had contacts with Mohammed Atta, who headed a Hamburg cell of Islamic extremists before leading the September 11 hijacks and suicide attacks. He was later released due to insufficient evidence.

German news magazine Der Spiegel reported that six members of the German intelligence services interrogated Zammar at length in Syria's Far Filastin prison in November 2002.

Alleged torture after CIA rendition

Zammar is suspected of being one of a growing number of detainees flown by the CIA from their point of capture to a third state, such as Syria, under Washington's policy of "rendition" where interrogation and torture are undertaken. "He has been subjected to beating and torture I cannot even describe," Husni said. Zammar was visited once by Red Cross officials.

The suspected collaboration of the German and American intelligence services in the Zammar affair forms part of the brief of a parliamentary inquiry currently under way in Germany. "The Germans had him," Husni said. "They would not have let him go if he had anything to do with the attacks."

Der Spiegel reported that the CIA and the US Federal Bureau of Investigation had asked Germany's BKA criminal police several times in late 2001 for information on the Hamburg-based Zammar, his identity, his previous history, and his environment.

At the end of November 2001, the BKA replied that it was closely monitoring his presence in Morocco and he planned to take a flight with Dutch airline KLM heading back to Germany on December 8.

On the orders of the CIA, the suspect was arrested at Casablanca airport. Two weeks later he was transferred to Syria.