Targets of the investigation led by the Munich prosecutor's office were nine German citizens between the ages of 25 and 47 years old, according to the state Office of Criminal Investigation in Bavaria. The men, most of whom have an immigrant background, are suspected of sedition and running a criminal organization.
No arrests were immediately reported.
Bavarian Interior Minister Joachin Herrmann told German news agency DPA the searches were a sign of the hazards of fundamentalist Islam.
More than 130 officers searched 16 buildings, including private flats, cultural centres and a publishing house in Neu-Ulm, Ulm, Sindelfingen, Bonn, Berlin and Leipzig.
DPA cited unnamed German security officials in a report that the suspects, including two imams, had tried to incite jihad among young Muslims using the internet and seminars on Islam. The suspects are accused of forming an organization dedicated to radicalizing German Muslims in September 2005, DPA reported.
The news agency reported that the offices of publisher As-Sunna were searched in Berlin and association rooms were searched in Leipzig. It linked the investigation to the Multi-Kultur-Haus, a multicultural centre in Neu-Ulm shuttered by German authorities in 2005, and to the Islamic Information Centre of Ulm, which the agency said is also suspected of support for radical Islam.