A group of Islamic radicals have been charged with planning to kidnap a French judge.
Prosecutor Francois Molins said that the Forsane Alizza group, or Knights of Pride, did physical training in parks and forests, collected weapons and preached hate and violence on their internet site, showing clips of Osama bin Laden.
The site was shut down after authorities banned the group in March.
Mr Molins said the investigation showed the network was organised around Forsane Alizza leader Mohammed Achamlane.
He stressed the group had no link to the killing spree last month in Toulouse that left seven dead. Suspected gunman Mohamed Merah was killed in a police stand-off.
The 13 - among 17 suspects detained in police raids last week - faced preliminary charges of criminal association linked to a terrorist network, a sweeping charge with a maximum 10-year prison term that is used in France to ensure a full investigation of terror suspects. Nine of the 13 are being held in jail. Charges of acquiring, transporting and detention of arms also were issued.
The remaining four who had been detained were being released.
The prosecutor said several terror plans appeared to be in the works, including the kidnapping of a judge in Lyon. An official close to the investigation said the targeted judge is Jewish.
Mr Molins said: "All the suspects confirmed Mohammed Achamlane's role of animator, co-ordinator and emir and his constant concern about acquiring weapons."
He said the plan to kidnap a judge who dealt with a child abuse case of a member of the Lyon cell was hatched at a September meeting. The magistrate in question has been placed under police protection.
Other potential targets included people from groups that have spoken out against the Muslim community, the prosecutor said.
Police found stashes of weapons during their raids last Friday in the Paris region and the cities of Nantes, Marseille, Nice, and Toulouse as well as documents and computer equipment. The probe so far has shown that members had consulted internet sites showing how to make explosives, Mr Molins said.