BERLIN (Reuters) -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.