French authorities have for the first time confiscated the passports of six nationals who were allegedly planning to travel to Syria tojoin jihadists.
Interior Minister Bernard Cazeneuve said the intelligence services believed the men wanted to join the Islamic State (IS) militant group.
The measure is part of new counter-terrorism laws adopted last November.
Meanwhile, France has deployed an aircraft carrier off Bahrain to be used against Islamic State (IS) militants.
Planes from the Charles de Gaulle carrier will be used against IS positions in Iraq, a spokesman for Defence Minister Jean-Yves Le Drian said.
The first Rafale fighter jet took off on Monday morning from the carrier as it sailed about 200km (120 miles) off the northern coast of Bahrain.
Correspondents say that the deployment of the warship will halve the time it takes for military aircraft - which normally fly from the United Arab Emirates - to reach Iraq.
France began Operation Chammal in support of the US-led coalition against IS in September.
Phone hotline Mr Cazeneuve said authorities had acted against the six men after their departure to Syria appeared to be imminent.
Their passports and identity cards have been confiscated for six months, after which the order can be renewed. They have the right to appeal against the move in court.