The operation took place in the small town of Lunel east of Montpellier in southern France, from where around 20 young people have left for Syria. Six of them, aged 18 to 30, have been killed since October.
Crack French security forces launched the operation at 6:00 am (local time) in a building in the centre of the town, according to witnesses that spoke to AFP.
"Several unmarked cars drew up. Masked men got out and smashed in the doors to the apartments in the building," said one resident of the block, who said they had threatened him.
Another witness said authorities had taken away his brother.
"They flattened me, got me on the floor, hit me. Then they took away my brother," this man said.