One of the men, reportedly known as Ilyass Boughalab, is believed to have been killed in Syria, while the second served a short prison sentence in Belgium for terror-related offences in 2014.
With an extensive understanding of nuclear facilities, the convict’s short jail sentence has raised further questioned of the Belgian security services as well as fears he may have passed on important knowledge about the sites to the terrorist group.
The shocking revelations come after the police claimed that the death of a security guard at a nuclear facility is being treated as a criminal act rather than a terror act.
Didier Prospero, who worked for G4S security at a Belgian nuclear research centre, was shot several times in the bathroom of his home in Froidchapelle, in the Charleroi region of Belgium.
His three children found his body after they returned from school on Thursday. Mr Prospero’s sheepdog Beauce was reportedly lying dead next to him.