French President Francois Hollande led Paris in a moment of silence for the victims in the deadly attacks on the city.
Earlier, police raided homes of suspected Islamist militants across France overnight, and a source close to the investigation said a Belgian national in Syria was suspected of orchestrating Friday's mayhem.
Prosecutors said one of the killers had been stopped and fingerprinted in Greece last month, fuelling speculation the Islamic State had taken advantage of the recent influx of refugees fleeing the Middle East to slip militants into Europe.