Spanish police said Friday they had detained a Syrian man suspected of funneling money to European jihadists linked to ISIS so that they could return to Europe.
Accused of "financing terrorist activities," the man was detained on Tuesday at his home in Madrid and remanded in custody the following day, a police spokesman said.
He was allegedly a go-between who would send "money from jihadist supporters to Syria" to help members of ISIS return to Europe, police said in a statement.
The money was mainly moved about by the "hawala" system, an informal method of payment based on trust that is far more difficult to trace than bank transfers.
The foreign fighters would use social networks to ask their supporters to finance their trip.
This operation "is part of the fight against the new strategy of Daesh which after its loss of territorial control asked its members to return to their countries of origin," police said, using an Arabic acronym for ISIS.
An estimated 40,000 people travelled from around the world to take up arms for ISIS as it occupied territory in Syria and Iraq and declared a caliphate in 2014.
Now that it has lost that territory, the big question is how many ISIS foreign fighters remain, and where they are.
Some have gone to other jihadist fronts like the southern Philippines, others are thought to be laying low, waiting for an opportunity to infiltrate themselves to Europe.
Repatriation of citizens who went to fight in Syria and Iraq is a hugely sensitive issue in Western nations that have suffered several jihadist attacks.