France to jail IS militants returning from Syria

France's government is preparing for an influx of homegrown militants amid a departure of US troops from Syria, warning anyone who left to fight for the Islamic State group will go straight to jail.

In an interview with BFM television, Interior Minister Christophe Castaner said that a handful of French militants had already returned and more would follow soon. Neither he nor France's foreign ministry confirmed BFM's report that as many as 130 could come back within weeks.

"The Americans are leaving Syria. It's important to keep that in mind," Castaner said. "There are a certain number who are imprisoned because the Americans are there, and they will be freed. They will want to return to France."

The question of what to do with foreigners who joined the Islamic State group has grown increasingly thorny as the US departure looms.

French militants made up the largest contingent of European recruits, and in 2015 and 2016 an Islamic State cell of French and Belgian fighters who sneaked in from Turkey attacked Paris and Brussels.

Britain refuses to take back citizens who joined the group and has stripped their citizenship. Other European countries have remained largely silent about the fate of men and women whom many see as a security threat.

"These are people who have voluntarily joined a terrorist organisation ... that has committed attacks in France and continues to threaten us," France's foreign ministry said.

Castaner said all would be jailed immediately in France and face trial, but declined to provide details.

Kurdish authorities in Syria have detained 900 foreign members of the group, and 4,000 family of IS members, according to Ilham Ahmed, a senior Syrian Kurdish official. Russia has taken some of the recruits back and jailed them.

The Syrian Observatory for Human Rights said there are at least 78 French women and children who had recently come out of the last stronghold of IS in eastern Syria. This is in addition to another 65 previously evacuated from other IS held areas and in Kurdish custody. It was not clear if Castaner was also speaking of civilians and families of IS members.

Castaner said a small number had already returned to France, although it's not clear whether they had voluntarily surrendered or were repatriated, or whether he meant fighters or their families.

In April, then US Defence Secretary Jim Mattis said French special forces had joined American troops in Syria.

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