Three Frenchmen returning from Syria were charged with planning terrorist acts.
The trio include the 29-year-old brother-in-law of Toulouse jihadist Mohamed Merah, who was shot dead by police after he murdered seven people, including a rabbi and three Jewish children, in a 2012 killing spree at a Jewish school.
The three men were being charged with "criminal association with the aim of planning terrorist acts". They were remanded in custody.
The men were initially arrested in Turkey, reportedly on suspicion of being part of a network that recruited jihadists for Syria. But in a series of glaring mishaps, they were allowed to walk free after arriving in France.
First, French authorities announced Tuesday they had arrested the men upon their arrival at Paris's Orly airport. Then it turned out the men had not flown to Paris at all.
In fact, Turkish authorities had placed them on a plane to the southern city of Marseille, where they were -- to their great surprise -- able to leave freely after being released from Turkish custody.
In a further bungle, passport control failed to flag the men as suspicious, as a security databank was out of order at the time.
French and European authorities are wary about nationals who have travelled to Syria and Iraq – where the radical Islamic State militant group controls large areas – and fear they may return to stage attacks on home soil.
Mehdi Nemmouche, the Franco-Algerian who stands accused for the killing of four people at the Jewish Museum in Brussels last May, spent one year with terrorist groups in Syria.
According to the EU's counter-terrorism chief, the number of European jihadists fighting in Syria and Iraq has risen to more than 3,000. Gilles de Kerchove has warned of a possible terror attack on European soil as Western powers ramp up their assault on the Islamic State terror group in Iraq and Syria.