The stunning revelation came into the spotlight earlier this week after Germany’s Focus magazine published a report citing an assessment of the domestic intelligence agency, the BfV.

Responding to Focus’ request for comment, the BfV, the agency in charge of monitoring extremist groups threatening constitutional order, said the number of Reichsbuerger (Citizens of the Reich in German) members had grown to 15,600 as of January – with the figure marking a dramatic increase of more than 50 percent within one year.

The highest number of extremists is in Bavaria, where the authorities recorded about 3,500 “Reich Citizens.” The former hotbed of German Nazism is followed by the state of Baden-Wuerttemberg with 2,500, and North Rhine-Westphalia with 2,200 members. Further down the list are Lower Saxony with 1,400, and Saxony with 1,300 Reichsbuerger.

In addition, the extremist movement is reportedly nurturing plans to set up an armed wing and stage violent acts, Focus reported. “They have begun preparing themselves for Day X,” an unnamed security official told the magazine, allegedly referring to a day of reckoning or uprising against the government.

The Reichsbuerger, a loose association of nationalist groups spread across the country, believe that modern-day Germany and its political institutions are run by a puppet government installed by the victors in World War II, which makes them illegitimate.

Many members of the group are considered to be on the extreme right. They maintain that the old German Reich – which ceased to exist in 1945 after the capitulation of Nazi Germany – should be restored in its pre-1937 borders, which included large swathes of land in Poland, Czech Republic and other neighboring countries.

In the past, members of the Reichsbuerger movement were often perceived as eccentric conspiracy theorists, but a string of attacks on police prompted the German government to take aim at the extremists.

The radical movement made headlines both nationwide and internationally in October last year, when a 47-year-old gun enthusiast, Wolfgang P., shot and killed a rapid response police officer on his doorstep.

On the day the shooting happened, police officers arrived at Wolfgang P.’s house in the Bavarian town of Georgensgmuend, when the man, already armed with a loaded shotgun and wearing a kevlar vest, began shooting, firing 11 rounds in total. Three officers were injured, and one would later die in hospital.

In August 2016, Adrian Ursache, a former Mr Germany winner, opened fire at officers and was injured during a police raidon the house belonging to his parents-in-law, which he had proclaimed an autonomous state, ‘Ur’. In May 2014, police in Rhineland-Westphalia arrested the self-declared ruler of an imaginary state called ‘Germanitia’.