Members of a far-right group in Germany arrested last week were plotting "shocking" attacks similar to last year's Christchurch massacre, a German government spokesman has said.
Twelve men belonging to Der harte Kern (The Hard Core) were arrested on Friday, with four accused of forming the group and the remainder of providing support.
Interior ministry spokesman Björn Grünewälder spoke about the speed with which the group formed.
"It's shocking what has come to light here, and that there are cells which appear to have become radicalised in a very short length of time," he said.
Prosecutors described the plot as involving "mosque massacres" inspired by the March 15 attacks that killed 51.
• Christchurch mosque attack livestream: Why Facebook continues to fail
• Christchurch mosque shootings: Accused will be among the first to read Royal Commission's report
• Christchurch mosque shootings: Accused gunman Brenton Tarrant pleads not guilty
• Christchurch mosque attacks: NZ media focused on the victims, Australian media focused on alleged gunman
The arrests are the culmination of months of undercover investigation, in which the alleged ringleader, Werner S, was heard detailing plans for "commandos" to groups of Muslims across Germany, news magazine Der Spiegel reported.
He said the men needed to be "intelligent, hard, brutal and fast".
The investigation revealed that the attacks were designed to provoke retaliation which the group wanted to spiral into civil war.
Raids on the group uncovered a large weapons cache, including firearms, grenades, crossbows and even spiked maces.
Aiman Mazyek, chairman of the Central Council of Muslims in Germany, called for more security at mosques across Germany.
He told Berlin newspaper Taz: "Without state protection, the situation is getting ever more dangerous. What are the security authorities waiting for?"
Steffen Seibert, spokesman for Chancellor Angela Merkel, said the government would protect all religious groups.
"It is the task of the state and naturally of this government, to protect the free practice of religion in this country, regardless of what religion that might be.
"Anyone practising their religion in Germany within our legal framework should be able to do so without being endangered or threatened."