Twenty-five people have been arrested in raids across Germany on suspicion of plotting to overthrow the government, writes BBC.
German reports say the group of far-right and ex-military figures planned to storm the parliament building, the Reichstag, and seize power.
A minor aristocrat described as Prince Heinrich XIII, 71, is alleged to have been central to their plans.
According to federal prosecutors, he is one of two alleged ringleaders among those arrested across 11 German states.
The plotters are said to include members of the extremist Reichsbürger [Citizens of the Reich] movement, which has long been in the sights of German police over violent attacks and racist conspiracy theories. They also refuse to recognise the modern German state.
An estimated 50 men and women are alleged to have been part of the group, said to have plotted to overthrow the republic and replace it with a new state modelled on the Germany of 1871 - an empire called the Second Reich.