The arrests were made in Naples, Salerno south of Naples and Latina, about 40 miles south of Rome, the Italian news agency ANSA reported. The charges included participating in political brawls in Naples in 2011, possessing arms and explosives illegally and attacking a left-wing group's clubhouse with Molotov cocktails.
Naples Assistant Prosecutor Rosario Cantelmo said members of the group had been secretly taped at meetings.
One of the suspects is Emanuela Florino, daughter of former Sen. Michele Florino, who represented the now-defunct Alliance Party. She was placed under house arrest.
One group targeted by the investigation is Casa Pound, which took its name from Ezra Pound, the U.S. poet who became an admirer or Benito Mussolini and made broadcasts for the Fascist government during World War II. Gianluca Iannone, the group's leader, accused prosecutors of trying to sabotage Casa Pound's effort in national parliamentary elections by keeping the group from "tackling the campaign with due serenity and on an even footing with other parties."
"They will not succeed," Iannone added.