Anouar Haddouchi was captured by Syrian Kurds after the fall of the last Daesh holdout in the eastern Syrian village of Baghouz in spring, the Belgian daily De Morgen has learned.
The 35-year-old, also known as the "executioner of Raqqa", is being probed by Belgian prosecutors for sending money to the mastermind of the 2015 Paris attacks and the 2016 Brussels bombings.
He is being held by the Syrian Democratic Forces together with his 32-year-old Belgian wife, Julie Maes. It is unclear whether he will be put on trial in Syria, Belgium or France, the daily said.
The Daesh terror organisation seized huge territories in Syria and Iraq in 2014, which were later retaken by the countries' governments. The organisation has also claimed responsibility for a number of terror attacks globally.
*Daesh (also known as ISIS/ISIL/IS) is a terrorist group banned in Russia