The arrests, ordered by prosecutors in Rome, came a day after a man in Florence with far-right leanings killed two Senegalese street vendors and injured another three, before fatally shooting himself.

Authorities did not immediately mention any link between the gunman, Gianluca Casseri, a 50-year-old author of fantasy literature, and Wednesday's arrests.

Police carried out the arrests in dawn raids in Rome, targeting members of the group, Militia.

Those detained also face charges of being apologists for fascism. Another 16 alleged members of Militia - including a 15-year-old - have been placed under investigation.

Prosecutors said in their arrest warrants that the suspects "wanted to lay the foundations for a revolutionary war."

The suspects are also accused of issuing threats against the leader of Rome's Jewish community, Riccardo Pacifici, and the speakers of Italy's houses of parliament - Renato Schifani of the Senate and Gianfranco Fini of the Chamber of Deputies.