German police have raided premises nationwide linked to an anti-Semitic far-right movement called Reichsbürger (Citizens of the Reich).
Neo-Nazi propaganda and firearms were seized in the raids, in 10 of Germany's 16 states.
The targeted group, "United German Peoples and Tribes", is part of Reichsbürger, whose members reject the German state as a legal entity.
The interior ministry said racism "even in times of crisis" would be combated.
The statement from ministry spokesman Steve Alter was a reference to the coronavirus pandemic, which has triggered the closure of German schools, businesses and public events.
The Reichsbürger movement is estimated to have 19,000 members in Germany. Those targeted are suspected of spreading racist threats and propaganda.
It is the first time the interior minister has banned a group associated with the Reichsbürger movement.
Last month a gunman linked by the authorities to far-right conspiracy theories murdered nine people of foreign heritage in the western town of Hanau.
In October 2017 a Reichsbürger member was sentenced to life imprisonment in Bavaria for killing a policeman during a raid on his home in 2016.
Thursday's raids were the latest big move against far-right groups this year. The authorities have also put part of the far-right political party Alternative for Germany (AfD) under systematic surveillance and banned the neo-Nazi group Combat 18.
Reichsbürger members do not recognise the post-war German federal republic, seeing it merely as some sort of private company. They believe in the continued existence of a German empire, or Reich, dating back to 1937 or even earlier. They are Holocaust deniers who espouse racist conspiracy theories.