A man was arrested on Friday over a serious sexual assault on an 11-year-old girl that stoked fears of a possible serial attacker in a popular holiday area of central France.

Campsites in the Ardeche region had been told to step up security following Wednesday's attack on the girl that has been linked to a string of similar assaults at campsites in recent weeks.

The 32-year-old suspect was arrested "without difficulty" at his home in Privas, the capital of the Ardeche region, and taken into police custody, the public prosecutor in charge of the probe, Franck Alzingre, told AFP.

The man, "who comes from the centre of the Ardeche", was "suspected of rape and sexual aggression against a minor," Alzingre said, without making it clear whether the rape accusation concerned the girl in the campsite.

Alzingre had said earlier that there was no evidence of a link between the latest attack and other incidents which have occurred on campsites in the area since the end of June.

"At the moment we have not established a link between this week's attack and the other cases but we are not ruling out any avenue of investigation," he told reporters.

Although Alzingre played down suggestions a serial rapist could be operating in the region, he confirmed that a squad of 50 officers has been assigned to the case, far more than would normally work on a single crime.

The girl was attacked by a man in the early hours of Wednesday as she slept in a tent alongside her younger sister on a campsite at Saint-Didier-sous-Aubenas in the south of the Ardeche.

Police had earlier said that as many as seven girls between the ages of seven and 12, one of whom was Dutch, had been attacked in the area in the past six weeks.

The manager of the campsite where the attack took place was reluctant to speak to an AFP reporter, but owners of other sites confirmed that they had taken steps to ensure the safety of their guests.

These include the deployment of nighttime guards and requiring campers to wear wristbands, making it easier to identify registered holiday-makers.

Michele, the owner of a site at Vogue-en-Ardeche, said she was telling parents to keep an eye on their children but not to panic.

"I speak to people, I tell them to be vigilant, to look out for their children," she told AFP. "Sometimes people can be too laid-back: we're not a creche or a kindergarten."

Christine Blanc, the president of the regional federation of campsites, called for a calm response to a situation that could have a serious impact on the tourist trade on which the remote region depends.

"For us, the theory of a serial rapist remains a rumour for the moment," she said.

The Ardeche is one of France's best-preserved wilderness areas and its river gorges and rich flora and fauna draw campers from all over Europe.