German authorities expect further arrests and raids in the coming days in connection with a far-right group that prosecutors say were preparing a violent overthrow of the state to install a former member of a German royal family as national leader.

"Based on my experience, there is usually a second wave of arrests," Georg Maier, the interior minister of the eastern German state of Thuringia, told broadcaster Deutschlandfunk.

The envisaged new leader Heinrich XIII P.R., who uses the title prince, is a descendent of the royal House of Reuss in Thuringia.

25 members and supporters of the group were detained yesterday in raids involving some 3,000 security personnel that Mr Maier described as unprecedented in modern German history.

Holger Muench, head of the federal police office, told broadcaster ARD that the number of suspects in the case now stood at 54, and that that figure could rise further.

"We have identified further people where we are not sure yet what their status is in connection with this group," he said.

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In their raids yesterday police found equipment ranging from protective vests to crossbows, rifles and ammunition, Mr Muench said, as well as plans to build up a "homeland protection command" and evidence of recruitment.

"We have a dangerous mixture of people who are following irrational convictions, some with a lot of money, others in possession of weapons and a plan to launch attacks and expand their structures," mr Muench said.

Mr Maier singled out the far-right Alternative for Germany (AfD) party, which is in the state parliament, for becoming an interface for right-wing extremists and spreading what he called fantasies about toppling the state.

"People are scared, and the AfD takes advantage of that and offers simple solutions," he said.

Yesterday the AfD had in a statement condemned the far-right group's efforts and expressed confidence in the authorities' ability to bring clarity to the situation quickly and completely.