Its members, who reject the legitimacy of the German republic, have long been dismissed as malcontents, crackpots and followers of esoteric beliefs, but they are seen as a growing threat after several have opened fire on police.
Police commandos targeted six residences and the seat of a so-called "Association for Bioenergetic Life" located in a former restaurant, all in North Rhine-Westphalia state.
They confiscated "three firearms, including a shotgun leaning, ready for use, by the front door" as well as home-made guns, gunpowder and ammunition, police said in a statement.
Officers also made two arrests of movement members on unrelated charges - a 53-year-old suspect, who was injured in a struggle, and his wife, 52, who was said to be in shock.
"Police were forced to shoot dead an aggressive Doberman for their own safety," police added in their statement.
The Reichsbürger include conspiracy theorists, neo-Nazis and gun enthusiasts who generally believe in the continued existence of the pre-war German Reich, while some idolise Nazi Germany.
Several groups have declared their own mini-states, made flags and issued their own identity papers, currencies and postage stamps. They often come into conflict with authorities because they refuse to pay taxes and fines.
Several Reichsbürger have opened fire on police, hoarded weapons and explosives, and allegedly plotted attacks against state institutions, migrants and members of the Jewish community.
Domestic intelligence service chief Hans-Georg Maassen said Wednesday the "Reichsbürger scene" of activists and sympathisers was now thought to number about 10,000, including 500-600 right-wing extremists and 700 with gun licences.
The community was growing more "radical" via social media and displayed "a considerable willingness to employ violence", Maassen said in a statement.
In an attack last August, a 41-year-old Reichsbürger and one-time "Mister Germany" pageant winner opened fire on police carrying out an eviction order at his house in the eastern state of Saxony-Anhalt.
The gunman was seriously wounded and three police officers suffered light injuries.
Another Reichsbürger is accused of shooting dead a police officer and wounding three others during a raid to confiscate his hunting weapons in a Bavarian town in October.