A plane carrying individuals for a skydiving trip has crashed in southern Belgium, killing all 11 people aboard, officials said.

Twenty minutes after the aircraft took off from a small airfield on Saturday close to Namur, witnesses suddenly saw the plane lose height very quickly, then crash in a field near Fernelmont town, said its mayor, Jean-Claude Nihoul.

The skydivers "were not able to jump out," Nihoul said in a telephone interview.

Ten skydivers and the pilot were killed and no one was hurt on the ground, he said, adding that three parachutes were found near the crash site.

Prime Minister Elio Di Rupo immediately confirmed the news of the crash and said his thoughts are with the families of the victims.