The number of supporters of the Reichsbuerger (Citizens of the Reich) movement has risen to at least 4,500 according to the Rheinische Post newspaper, citing information from German state interior ministers and intelligence chiefs.
The recent figure has sparked concern in Germany, with previous surveys putting the movement's supporters at the much smaller figure of 1,100.
According to @rponline, there are at least 4500 followers of far-right Reichsbürger movement in Germany, who dont recognize federal gov— Ira Spitzer (@IraSpitzer) December 13, 2016
The Reichsbuerger movement, which has no distinct leader, hierarchy or ideology, has been traditionally thought to have consisted of people sharing racist, anti-Semite or right-wing extremist views, united by one thing: their refusal to recognize the authority of the German state.
In denouncing the legitimacy of modern Germany and supporting the continuation of the German Reich, some supporters adhere to national borders lines of 1937, despite the defeat of Nazi Germany in World War Two.
Echoing similar movements in the US and other countries, some Reichsbuerger followers often refuse to pay taxes or fines, others use homemade identification and registration plates, while one member even created his own self-proclaimed kingdom and starting printing his own money.
'Threat to Our State'
While stories about the movement are not new in Germany, there are concerns that the Reichsbuerger movement is growing increasing violent, with a follower shooting dead one police officer and wounding three others during a shootout near Nuremberg in October.
Soon after police discovered a weapons stockpile believed to belong to the group, which led to the movement being placed under surveillance by German intelligence agencies, amid reports that some Reichsbuerger supporters were in Germany's police force.
CDU politician Stephan Harbarth told the Rheinische Post that authorities should not underestimate the group, saying they are not "harmless crackpots", but a "threat to our state."
The comments echoed recent warnings made by German Interior Minister Thomas De Maiziere, who highlighted the rise in support for the movement.
The FARC peace agreement in Colombia, the Brexit in UK, even Germany is seeing a revival of right wing extremism.— b (@biancavivion) November 10, 2016
"The danger emanating from this group has significantly increased over the last year. It is time to take a closer look at what they are doing."
The comments over the Reichsbuerger movement come as German intelligence authorities keep a close eye on any signs of domestic terrorism, with authorities warning of a rise in support for extremist groups in recent times.