Interior Minister Hans-Peter Friedrich said he had banned the Salafist organization Millatu Ibrahim, saying it has been calling on Muslims to fight against Germany's "constitutional order."
The raids, conducted by 850 police officers in seven of Germany's 16 states, focused on two other groups—DawaFFM and DWR—to determine whether evidence exists to ban them as well. DWR's initials are the German abbreviation for "The True Religion.
Friedrich said a "comprehensive collection of evidence" had been seized—videos, laptops, cellphones and other items. "All these things will be evaluated over the coming days, and we will see to what extent the evidence is sufficient to ban the two organizations which are being investigated," he said.
Friedrich said authorities believed there were preparations under way to replace the German constitutional state with Sharia law, and warned that anyone who does so can expect to face prosecution.
Among other things, Millatu Ibrahim taught followers to reject German law and follow Islamic Shariah law and that "the unbelievers are the enemy," a German security official said on condition of anonymity because of the sensitivity of the issue.
Germany's intelligence and security agencies have increasingly been monitoring the actions of the Salafists, who number some 4,000 in Germany, in recent months.
That monitoring was intensified in May, after street clashes between Salafists and the small far-right Pro NRW party in Bonn and Solingen, in western Germany.
Following the fights, a video surfaced online by a known terrorist, Bonn-born Yassin Chouka—who is believed to be with the Islamic Movement of Uzbekistan in the Afghanistan-Pakistan border region—calling for members of Pro NRW and German media to be killed. He urged the Salafists to move away from street confrontations where the risk of being arrested was too great and instead to target Pro NRW members at their homes and workplaces.
That prompted officials to worry the message could inspire a lone-wolf type attacker like Arid Uka, an Islamic extremist who killed two U.S. airmen at Frankfurt airport last year after being spurred to action in part by a YouTube video preaching jihad, or holy war.
So far, however, "we don't have any intelligence of concrete attacks planned," the German security official said.
Authorities are now braced for more possible violence on the streets, he said.
"We assume there will be protests against these measures," he said. "We'll have to see how they play out."
Geir Moulson contributed to this story