About 1,000 police raided scores of buildings across Germany on Thursday in a clampdown on Salafists.
German authorities have recently stepped up their monitoring of Salafist groups.
In May Salafists turned on police protecting far-right anti-Islam protesters during a regional election rally in the west German city of Bonn.
The far-right protesters had infuriated the Salafists by waving cartoons of the Prophet Mohammad.
Salafists are believed to number about 4,000 in Germany, which has a total Muslim population of some four million.
Announcing the crackdown, Interior Minister Hans-Peter Friedrich said he had banned one of the Salafists' groups called the Millatu Ibrahim and said the raids may unearth evidence that would allow the outlawing of two other associations.
"(The Millatu Ibrahim group) works against our constitutional order and against understanding between peoples," Friedrich told reporters.
Thursday's raids targeted about 70 apartments and communal houses of Salafists in Berlin, Hamburg and other cities.
Among the homes targeted was that of preacher Ibrahim Abu Nagie, who is associated with a campaign to distribute free copies of the Koran.