A Belgian national currently in Syria and believed to be one of Islamic State's most active operators is suspected of being behind Friday's attacks in Paris, according to a source close to the French investigation.
"He appears to be the brains behind several planned attacks in Europe," the source told Reuters of Abdelhamid Abaaoud, adding he was investigators' best lead as the person likely behind the killing of at least 129 people in Paris on Friday.
According to RTL Radio, Abaaoud is a 27-year-old from the Molenbeek suburb of Brussels, home to other members of the militant Islamist cell suspected of having carried out the attacks.
Media in Belgium said Abaaoud had been involved in a series of planned attacks in Belgium foiled by the police last January.
At the time, Belgian police in the town of Verviers killed two men who opened fire on them during one of about a dozen raids against an Islamist group that federal prosecutors said was about to launch "terrorist attacks on a grand scale".
At the moment of the Verviers events, Abaaoud's cellphone was located in Greece, RTL said. While there was no clear link established, French prosecutors said fingerprints from one of the suicide bombers matched the prints of a man registered in Greece in October.
In February of this year, Islamic State's online magazine Dabiq carried an interview with an Islamist bearing the name of Abdelhamid Abaaoud and boasting of having traveled through Europe unnoticed by security forces to organize attacks and procure weapons.
Abaaoud was also named in various media last year as the elder brother of a 13-year-old boy who left Belgium to become a child-fighter in Syria.
Interviewed by Belgian newspaper Het Laatste Nieuws earlier this year, their father Omar Abaaoud disowned his older son.
"Abdelhamid has brought shame to our family. Our lives are equally destroyed. Why would he want to kill innocent Belgians? Our family owes everything to this country," he said.