At this point, it's still unclear whether the fighter posted the video himself. He is said to be in the city of Aleppo in northern Syria, where the rebels have clashed with government troops.
One of the sites named as a potential target for a murderous outrage is the Atomium, a Brussels landmark.
The text reads: "Bombs are falling. Atomium, I hear a bang. Body parts everywhere!"
The video includes threats against the Belgian Defence Minister Pieter De Crem and the right wing Dutch lawmaker Geert Wilders: "De Crem, Wilders, the traitors are falling, watch out for cars loaded with explosives."
The video has meanwhile been removed from the video sharing website, but you can still see part of it in the Dutch language report below aired on VRT television.
The anti-terrorism unit operated by Belgian police is taking the threat seriously. Intelligence experts are currently examinig the message.