PARIS  - The 17 people detained by French police in a crackdown on suspected Islamist networks were on Sunday remanded in custody for at least another 24 hours, a source close to the inquiry told AFP.

Friday's arrests were made in connection with a probe into an alleged terror plot and under French anti-terror laws the suspects can be held without charge until Tuesday. The head of France's DCRI said on Saturday that those arrested were "French nationals" involved in "collective war-like training, linked to a violent, religious indoctrination."

Some of those arrested belonged to a suspected extremist group called Forsane Alizza, he said, and had been involved in paintball gun games.

The arrests took place in several cities, including Toulouse, where extremist gunman Mohamed Merah was shot dead by police last week after a series of cold-blooded shootings that left seven dead, including three Jewish children.

Socialist Michel Sapin on Sunday admitted that the arrests were "legitimate" but said that the presence of television news cameras during the roundup was not, after the footage was beamed into French homes.

"The presence of cameras at that moment to film the scene so that it can then be reproduced and comment on is not legitimate," Sapin told Radio J.