Osama Krayem, a Swede of Syrian origin, has been held in Belgium since 2016 and could face war crimes charges over the murder of Maaz al-Kassasbeh, whose grisly death was filmed and put online in an incident that came to symbolise some of the worst excesses of Isis.
Krayem is suspected of playing a key role in the jihadist cell behind the attacks in Paris, which killed 130 people, and Brussels, which left 32 people dead. Both were claimed by Isis.
Now investigators have linked him to the killing of Kassasbeh, who was captured when his plane came down in an IS-held part of Syria in December 2014.
“We have been able to establish that he was there,” a source close to the Belgian probe told AFP on Friday, saying Krayem could be prosecuted for a “crime against humanity”.
Krayem, like other members of the Paris-Brussels cell, travelled to fight for Isis in Syria in 2014 before apparently hiding himself among migrants in
order to return to Europe from Syria in 2015.
According to Belgian newspaper La Derniere Heure, Belgian police have identified Krayem as actively taking part in the killing.
The video of Kassasbeh's murder outraged Jordan, which stepped up air strikes on Isis and executed two convicted jihadists on death row in response.
Belgian investigators are considering the next move now that Krayem has been linked to the pilot's killing, the source told AFP. Information could be passed on to the Jordanian authorities.