PARIS France, waging war against Islamist extremists in Mali, is on the hunt for would-be fighters at home, fearful that they will join militants in the conflict in its former African colony or take radical action on French soil.
With Iraq and Afghanistan no longer magnets for foreign fighters, officials say they worry that some angry youth among the country's large Muslim population are instead looking to test their radicalized faith on the battlefield in Mali or the Syrian civil war.
Police have rounded up youths they suspect of trying to join Islamist extremists in West Africa, arresting four this week, and expelled radical imams and others considered risks to public order. Authorities, who have long viewed France's Muslim community of at least 5 million with a special lens, say they fear they could trigger a spread of radicalization among Muslims in disaffected suburban housing projects where unemployment and resentment against state institutions is rife.
Moderate Muslims express concern that sweeps against suspected Islamist extremists risk stigmatizing all Muslims in France.
In the latest case, authorities detained four people in a Paris suburb who are believed to have links to a Frenchman caught last year in Niger on the border with Mali as radical fighters were expanding their control in the region.
French authorities are trying to determine whether there were links among them, or to a budding network for sending fighters from France to the Sahara, a judicial official said on the condition of anonymity because an anti-terrorist investigation is under way.
"We must continue this work of dismantling these networks that want to act on our territory or sneak out individuals to carry out jihad," Interior Minister Manuel Valls said on French television Tuesday. "We are also fighting an internal enemy."
Trying to sell the country's military intervention to international partners, President Francois Hollande stressed from the outset that European security was directly at risk from radical Islamists and that Mali could become a sanctuary for global jihadists.
But no one knows how many foreign fighters went to Mali to join Islamists in their bid to transform the country and it is unclear whether the French invasion is inspiring more. Most of the foreign militants came from neighboring African countries, experts say, and there is general agreement that the number of Europeans who went to Mali before the war started is low.
Valls said on BFM-TV that there are "probably a handful" of French who went to Mali and authorities know of several who wanted to get there. Someone proven to be heading to combat zone risks being charged in France with preparing an act of terrorism.
Since the beginning of the intervention, French officials have repeatedly warned that the campaign has raised the risk that France becomes a target of terrorist anger. Dreaded scenarios include French citizens hardened in battle or driven by jihad continuing their mission on home soil, or spreading their message to Malian immigrants in France.