Molins said the suspects were accused of being part of a criminal group linked to a terrorist network and of illegally collecting weapons, France 24 reported.
Under French law, a formal inquiry precedes the filing of criminal charges.
Molins told reporters some of the men in custody told authorities that the kidnapping of a judge in Lyon had been considered. However, the prosecutor downplayed the threats, saying they were an "intellectual project" that hadn't been implemented, Le Figaro said.
French President Nicolas Sarkozy also downplayed the kidnapping reports, but called the information "plausible."
Forsane Alizza is a French pro-al-Qaida group banned earlier this year for encouraging French residents to go to Afghanistan to fight jihad.