German prosecutors say they have arrested 25 people suspected of being involved in a terrorist group that was allegedly plotting to overthrow the government.

Federal prosecutors on Wednesday mobilized about 3,000 officers to raid more than 130 locations in Germany, Italy and Austria. They detained 25 suspected members and supporters of the group of far-right and ex-military figures.

The prosecutors say a man they named as Heinrich XIII P. R. under Germany's privacy laws and an ex-serviceman are believed to be ringleaders. They say the arrested also include a judge who was a parliament member until last year.

They also say group members believe in a conspiracy theory that Germany is controlled by a so-called deep state and had been plotting a coup to establish their own government since around November last year.

The prosecutors suspect some members planned to storm the parliament building.

They say the group had a shadow cabinet and a military wing and was trying to recruit people in the German military and police.

The shocking news of the coup plot and the group's approach to security authorities has made headlines in the country.