Germany plans to tighten its gun laws in the wake of a suspected plot by a far-right group to violently overthrow the government and install a minor royal as national leader, its interior minister said in an interview published on Sunday.

German police last week arrested 25 people suspected of involvement in the plot, which has shocked many in one of Europe’s most stable democracies.

Prosecutors allege that many of the suspects were members of the Reichsbuerger (Citizens of the Reich) movement, which does not believe in the existence of the modern German state, according to prosecutors.

Interior Minister Nancy Faeser, in an interview with Bild am Sonntag newspaper, warned that the Reichsbuerger represented a rising threat to Germany given it had expanded by 2,000 to 23,000 people in the past year.

“These are not harmless crazy people but suspected terrorists who are now sitting in pre-trial detention,” Faeser was quoted as saying.

Prosecutors have said the suspects included individuals with weapons and knowledge of how to use them. They had attempted to recruit current and former army members and had stockpiled weapons.

“We need all authorities to exert maximum pressure” to remove their weapons, Faeser was quoted as saying, which was why the government would “shortly further tighten gun laws”.

Before the raids, authorities had already confiscated weapons from more than 1,000 Reichsbuerger members. However, at least another 500 are still believed to hold gun licences in a country where the private possession of firearms is rare.

The fact senior civil service members – such as former politician and Berlin judge Birgit Malsack-Winkemann – were among those arrested on suspicion of plotting has particularly shaken many in Germany.

Jochen Lober, the lawyer who defended her in a legal case in October where the Berlin government tried to force her to retire as judge, declined to comment on her arrest.

The Berlin branch of the far-right Alternative for Germany party, of which she is a member, said it did not know which lawyer was representing her and could not comment on her specific case until the investigation yielded results.

The interior ministry also wants to tighten disciplinary procedure for civil service members so it can more quickly fire them or withdraw their pension in the case of serious misconduct, sources familiar with the matter told Reuters. At the moment such procedures can last for years.