The seven men, some with beards, raised alarm in the eastern city of Strasbourg when they were seen acting out scenes of combat with fake weapons yesterday.
Police were called to the scene where they checked the men's identity documents and held one of them for questioning.
A police source said yesterday that the men had said they were "training to fight in the name of jihad".
According to a 35-year-old member of the group -- a Muslim speaking on condition of anonymity -- the man held was their self-defence teacher.
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"It was our first course, we hardly knew each other. We were doing some stretches, ran a few laps, practised body placement, punch-kick combinations," he said.
It was "simply a self-defence course with a trainer".
The men, aged between 30 and 45, then teamed up for a scenario in which they feigned an attack with fake guns and knives.
"This was not with the aim of going to Syria, we are far from all of that," he said.
French authorities are on high alert about nationals travelling to fight alongside extremists in Syria and Iraq.