Paris: Salah Abdeslam, a key suspect in November's Paris attacks, was put under formal investigation by French magistrates on Wednesday on charges of belonging to a terrorist organisation, murder, kidnapping and holding weapons and explosives.
He will be put in solitary confinement, lawyer Frank Berton said.
Abdeslam had been extradited to France from Belgium earlier in the day.
Abdeslam is believed to be the sole survivor among a group of militants who killed 130 people in Paris in November.
Abdeslam, 26, was Europe's most wanted fugitive until his capture in Brussels on March 18 after a four-month manhunt. He was taken by helicopter to Paris under armed guard and then driven to the capital's main law courts.
French Justice Minister Jean-Jacques Urvoas said Abdeslam would be held in a high-security prison in the Paris region.
His capture in March came four days before separate suicide bomb attacks by militants at Brussels international airport and on a metro train which killed 32 people.
Earlier, Berton, a high-profile French criminal lawyer, said he would lead Abdeslam's defence and had visited his client for more than two hours last week in his prison cell in Belgium along with Abdeslam's Belgian lawyer, Sven Mary.
Investigators say Abdeslam told them he arranged logistics for the multiple suicide bombings and shooting attacks in Paris and had planned to blow himself up at the Stade de France sports stadium before backing out at the last minute.
He is suspected of having rented two cars used to transport the attackers to, and around, the French capital.
"He told me naturally that he has things to say and he will say them. He wants to talk," Berton told BFM TV. "What counts and what matters for us as his lawyers is simply that he gets a fair trial, that he is sentenced for things he did and not things that he didn't do. That's vital because he is the sole survivor."
Abdeslam's elder brother Brahim blew himself up in a suicide bomb attack on one of several Paris cafes targeted by a group of assailants armed with AK-47 rifles and suicide vests.
Salah Abdeslam's confession to investigators suggested he may have been the 10th man referred to in an IS militant group claim of responsibility for the multi-pronged attack on the stadium and the Bataclan concert hall.
Police found an abandoned suicide vest in a rubbish bin in a Paris suburb after the attacks, fuelling speculation that it may have belonged to Abdeslam, who escaped by car back to Belgium hours after the attacks.
Abdeslam had been held in a prison in the Belgian town of Bruges. Last week, he was charged in Belgium over a shootout with police in an apartment in southern Brussels where his fingerprints were found days before his arrest.
Belgian police have arrested a number of his associates, including Mohamed Abrini, wanted over the Paris attacks and also a suspected Brussels attacker.
Sven Mary, Abdeslam's main defence lawyer in Belgium, said in a newspaper interview he had been subjected to verbal and physical assault since taking up a case that he might now drop.
Mary, who described Abdeslam as "gold dust" on the grounds that he was willing to talk, distanced himself from his client, telling France's Liberation: "He's a little jerk from Molenbeek, from a world of petty criminals - more of the follower than a leader, with the brains of an empty ash-tray."