The 29-year-old Frenchman arrested on Friday over the fatal shooting of three people at Brussels' Jewish Museum spent a year in Syria after becoming radicalised during the last of five stays in jail in France, a prosecutor said on Sunday.
When he was arrested in the southern France city of Marseille, Mehdi Nemmouche was carrying in his luggage weapons and clothes similar to those used in the shooting last weekend, Paris prosecutor Francois Molins told a news conference, saying there was a "strong body of evidence" tying him to the killings.
"During his last stay in jail he was noticed for extremist (Islamic) proselytism," Molins said. "On Dec. 31, 2012, three weeks after he was freed, he travelled to Syria."
"He spent over a year in Syria, where he seems to have joined the ranks of combatant groups, jihadist terrorist groups."
Nemmouche is being held on charges of murder, attempted murder and possession of weapons, all of which in the framework of a terrorist activity, Molins said.
Nemmouche has said nothing so far, he added.