Police conducted raids in search of suspected Islamist militants across France and in Belgium overnight following the Paris attacks, and a source close to the investigation said that 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, fueling speculation that the Islamic State group had taken advantage of the recent influx of refugees fleeing the Middle East.
The Paris carnage, in which 129 people were killed, has led to calls for the European Union to close its borders to asylum seekers.
On Monday, French President Francois Hollande said in an address to parliament that he will propose a law extending the country's state of emergency for three months.
Prime Minister Manuel Valls warned that France could behit by new violence, but he said Islamic State, which has claimed responsibility for the attacks in retaliation for French airstrikes in Iraq and Syria, would never win.
Interior Minister Bernard Cazeneuve told journalists on Monday that police arrested 23 people and seized arms including rocket launchers in 168 raids overnight. An additional 104 people were put under house arrest, he said.
"Let this be clear to everyone: This is just the beginning. These actions are going to continue," Cazeneuve said.
French warplanes pounded Islamic State positions in its Syrian stronghold of Raqqa late on Sunday - its biggest such strike since it began assaults as part of a US-led mission launched last year.
The investigation into the coordinated Paris attacks, the worst atrocity in France since World War II, led swiftly to Belgium after police discovered that two of the cars used by the militants had been rented in the Brussels region.
