The Public Prosecutor's Office and the State Criminal Police Office in Berlin are investigating 15 people on suspicion of forming a right-wing extremist organization.
On Wednesday there were searches in Berlin, Schleswig-Holstein, Baden-Württemberg and Hesse, as the authorities announced.
Firearms, alarm weapons, ammunition, cutting and stabbing weapons, data carriers, devotional objects of the association as well as narcotics and doping agents were confiscated at 14 locations, it said.
A total of about 130 police officers and a public prosecutor were involved in the action.
The 15 suspects are accused of being ringleaders or being a member of a criminal organization, the authorities said.
The main accused lives in Berlin.
Under his leadership, the suspects are said to have joined together in a right-wing extremist organization called the "Berserker Clan".
According to the authorities, the preparation for a "day X" played a role in the communication between the suspects again and again.
This should mean an armed uprising against the existing structures in Germany.
There was also some talk of firearms.