Wedged between a fitness center and a restaurant, the mosque called Masjid Taiba is a small, unassuming building in the central quarter of Hamburg. In the late 1990s, the mosque's prayer rooms became a cauldron of terror the place where Mohammed Atta and his "Hamburg Cell" henchmen congregated before the deadly 9/11 attacks. On Monday, Aug. 9, German police raided the mosque, confiscated dozens of computers and files and announced that because the spiritual home of several of the 9/11 hijackers had once again become a magnet for violent extremists, the mosque would be shut down.
"The Taiba mosque was the main meeting point for radical Islamic militants in Hamburg and had been supporting the international terrorist network for years," Manfred Murck, deputy director of Hamburg's intelligence service, tells TIME. "Young Muslim men were drawn to the mosque they met there, prayed, chatted together, became radicalized and set up extremist groups." Murck adds that the men came from different backgrounds, ranging from Moroccans and German Islam converts to militants from the former Yugoslavia, Chechnya and the Middle East. They all had one thing in common their commitment to jihad. "Some Muslims at the Taiba mosque had contacts with al-Qaeda," claims Murck.
Intelligence officials say the mosque had been under continuous surveillance since the 9/11 attacks. Back then, the mosque was known as al-Quds. Hijackers Mohammed Atta, Marwan al-Shehhi, Ziad Jarrah and Ramzi Binalshibh who according to U.S. officials was a key 9/11 facilitator and Atta's roommate were all regulars at the prayer house in the run-up to the 2001 attacks.
In March 2009, the Taiba mosque again became a location of special interest to investigators when a group of 11 Hamburg jihadists, mostly German men with roots in the Middle East and the Caucasus, traveled to Afghanistan and Pakistan to attend terrorist training camps. Officials say at least one man who lived in Hamburg, identified by the intelligence services as Shahab D., joined the militant Islamic Movement of Uzbekistan (IBU), which is believed to have close links with al-Qaeda. The Iranian-born man, in his mid-20s, appeared in a terrorist video in October 2009 under the name of Abu Askar; he urged other Muslims to join jihad and threatened attacks on Germany. Some members of the group ended up in Pakistani custody and were sent back to Germany, while other jihadists are still in Pakistani or U.S. custody.
Back at the Taiba mosque in Hamburg, intelligence officials say the men were treated as "heroes," and as other Islamic militants gathered at the mosque and tried to latch on to terrorist organizations in Afghanistan, a form of "jihad tourism" developed.
In the raids on Aug. 9, the Taiba German-Arab cultural association that ran the mosque was also banned by Hamburg's Interior Ministry, and the group's assets were seized, although no arrests were made in any of the day's raids. "We've closed the Taiba Mosque, as it was here that young men were converted into religious fanatics," Christoph Ahlhaus, Hamburg's Interior Minister, said in a statement. "Behind the scenes, an alleged cultural organization has shamelessly exploited the freedoms of our constitutional democracy to promote the cause of the 'holy war,' " he said, pointing out that the courses, sermons and seminars at the mosque "spread an ideology that was hostile to democracy" and sought to radicalize young Muslims. Ahlhaus insisted that Hamburg "must not serve as the incubator for Islamists willing to use violence."
The Taiba association could not be reached for comment about the police raids, but German media outlets have reported that in the past, the organization denied accusations of terrorist ties. According to the news magazine Focus, the group wrote in October 2009 that it was the "victim of a big media campaign, a bad secret-service plot and a concocted political farce."
As part of the police operation, investigators in the city searched four apartments and houses belonging to members of the Taiba association again, no arrests were made. German security sources tell TIME that one of the apartments searched on Monday belonged to Mamoun Darkazanli, a German-Syrian suspected al-Qaeda supporter who used to run an import-export company in Hamburg and is wanted in Spain on terrorism charges. Darkazanli was arrested in Hamburg in 2004 on a Spanish warrant but released in 2005 after a ruling by Germany's federal constitutional court. German intelligence officials say he was one of the imams at the Taiba mosque and have described him as a "hate preacher." "Darkazanli encouraged young Muslim men to join the jihad with his emotional prayers," says Murck. So far German prosecutors haven't been able to find evidence that he supported al-Qaeda.
Now that the mosque has been closed, fears have been raised that members could regroup and gather in other mosques in Hamburg. A large harbor city with a thriving immigrant community, Hamburg has acted as a haven for Islamic extremists in the past, as New York, Washington and Pennsylvania learned to their horror nearly 10 years ago. A 2009 intelligence report from German Domestic intelligence estimated that there are 2,000 Islamists in the city, of whom 200 are bent on violence and 45 are jihadists with links to other violent Islamic extremists in Germany and abroad. With one of their alleged meeting points closed, the challenge for intelligence agencies now is to prevent new terrorist cells from forming within their dispersed ranks.