German police have launched nationwide raids targeting ultra-conservative Islamic Salafists, suspected of posing a threat to public order.
Some 1,000 police officers were involved in searches that took place early on Thursday at Salafists' homes and meeting places in seven states.
A Salafist group called Millatu Ibrahim, based in the western city of Solingen, has been banned.
The raids follow clashes between police and some Salafists.
German authorities believe the Salafists want to create a Sunni Islamic caliphate opposed to Western democracy and that some of the group support martyrdom and using violence.
Raids took place in Bavaria, Berlin and North Rhine-Westphalia, among other states.
In one of the raids, police removed items from the home of Salafist preacher Ibrahim Abu Nagie in Cologne.
The authorities have been monitoring Salafist campaigns to recruit supporters, including the distribution of free Korans.
There are believed to be about 4,000 active Salafists in Germany, the state-owned broadcaster ARD reports.
The BBC's Stephen Evans, in Berlin, said that Germany has a track record of violent Islamism, with some of the men who took part in the attacks of 11 September 2001 having worshipped at a Hamburg mosque.
But, he adds, most of Germany's Muslims, most of whom are Turkish in origin, shun violence.