The Asayesh Kurdish security units detained Mohammed Haydar Zammar, a member of the so-called Hamburg Cell accused of helping to plan the September 11, 2001 attacks in New York, announced the Syrian Observatory for Human Rights and Kurdish officials on Thursday. Zammar, a Syrian-born German, was arrested in northern Syria and is now being interrogated by the security apparatus from the US-led coalition fighting ISIS in northern Syria. The Hamburg terror cell is thought to have been an important operative in the 9/11 attacks in the United States. In 2007, a Syrian court sentenced Zammar to 12 years in prison for being a member of the Muslim Brotherhood. He was later transferred from Syria’s Saadneya prison to the central prison in Aleppo. A Syrian opposition official told Asharq Al-Awsat he had met Zammar in jail. “He spoke little and did not voice his positions. I learned later he had joined ISIS,” the official said. In 2014, reports said Zammar was released as part of a “deal” reached between Damascus and extremist opposition factions. The deal stipulated the release of Zammar and five other extremists in exchange for detained Syrian regime officers. His whereabouts remained unknown until the Observatory and Kurdish officials uncovered on Thursday that they had captured him and others. Zammar is dubbed the “Syrian bear” for his immense size, weighing around 150 kilograms. He has played a leading role in the 9/11 attacks. The man is believed to have recruited from the mosques of Germany’s Hamburg some of the perpetrators of the New York attacks, including Mohammed Atta, Ziad al-Jarrah and Marwan al-Shahhi, who were sent to Afghanistan in 2008 before moving to the US to receive aviation training.