Security forces on Monday arrested seven men believed to be planning a terror attack in France and preparing to travel to conflict zones in Iraq and Syria, sources close to the case told AFP.
They were detained by France's DGSI domestic intelligence agency in the western coastal city of Brest and the surrounding Finistere region.
Some of the men were on the country's "Fiche S" list of potential security risks because of their links with Islamic extremists, one of the sources said.
Investigations will continue to determine how far the suspects had advanced in their plans for the attack and flight to the Middle East.
France has been on high alert since a wave of jihadist attacks that began in 2015 which have killed more than 250 people.
Dozens of French citizens left to join the Islamic State group in Syria and Iraq before US-led coalition forces dislodged the insurgents from their so-called "caliphate" last year.
IS leaders also urged followers in France to stage attacks on their own, often targeting security forces, and officials have said the threat of further IS-inspired attacks remains high.
French officials say they have foiled several terror plots in recent months.
Last May, police arrested a 16-year-old in the eastern city of Strasbourg as part of investigations into a suspected plot to attack security forces and possibly the presidential Elysee Palace.
Three adults and a teenager were arrested several weeks earlier over plans to carry out what Interior Minister Christophe Castaner said would have been an "extremely violent terror attack".