A 16-year-old French girl was arrested Saturday at the airport in Nice as she tried to board a plane to Turkey.

Officials say the teen intended to travel to Syria to join the Islamic State (IS).

Several hours before the teen's arrest, a 20-year-old man was arrested for recruiting the girl and purchasing her plane ticket. Allegedly, the girl's parents were unaware of her plans.

On Sunday, Interior Minister Bernard Cazeneuve urged parents to call a toll-free hotline if they observe "a disturbing trend of violent radicalisation" in their children.

The International Center for the Study of Radicalisation at King's College London reported that about 700 French citizens have defected and joined the extremist Muslim terrorist group in Iraq and Syria.

About 500 UK citizens, 300 Germans, 150 Australians, and over 100 Americans have also joined IS.

The French hotline was established four months ago and has received nearly 300 calls – one quarter of them relating to children. It is unclear how many arrests have stemmed from the tips.

Last week, the UK's terrorism threat level was raised from "substantial" to "severe" for the first time since 2011. Prime Minister David Cameron addressed Parliament on Monday, calling for more stringent anti-terrorism legislation. Cameron said that allowing police officers to confiscate passports at airports, and enacting other security measures will close "specific gaps in our armory".

The Australian government enabled its police officers to confiscate passports nearly two months ago.

"I've cancelled a number of passports on the advice of intelligence agencies," Australian Foreign Minister Julie Bishop said in June.

"We are concerned that Australians are working with them [ISIS], becoming radicalised, learning the terrorist trade, and if they come back to Australia, of course it poses a security threat."

US officials have not announced what measures they are taking to prevent more Americans from joining IS and other extremist Muslim groups.