German police have carried out raids in seven different states targeting individuals suspected of belonging to Islamic Salafist groups, the interior ministry said.
At the same time, Hans-Peter Friedrich, the interior minister, banned one particular network known as "Millatu Ibrahim".
Three ultra-conservative Muslim organisations were targeted in the raids early on Thursday, a ministry spokesman said, without providing any further details.
About 70 different premises were raided, including flats, mosques, schools and local associations, with the biggest operations taking place in the states of North Rhine-Westphalia and Hesse, the ministry said.
In a statement, the regional state interior minister of North Rhine-Westphalia, Ralf Jaeger, described the police operation as a "decisive step by the security services in the fight against dangerous extremists."
"Today's operation shows that we're turning up the pressure on the Salafists," Jaeger said.
At the beginning of May, German authorities opened an inquiry against 44 members of the Islamic Salafist community and 37 others after violent clashes with police in the western town of Solingen.
The Salafists have raised concern with their drive to convert non-Muslims, a campaign that has involved handing out 25 million copies of the Quran in Germany, Austria and Switzerland.
Authorities estimate there are about 2,500 Salafists in Germany. They espouse an austere form of Sunni Islam, but officials in Germany accuse them of also condoning violence against state institutions.