"There was a problem on takeoff and they tried to come back but unfortunately the plane crashed," said Melissa Milioto an airport spokeswoman. "Five people were killed."
Firefighters sprayed water on the plane that was reduced to a wreck of twisted metal, with only the tail still visible, TV images showed.
The Belgian news agency Belga said the five killed were three young children, their mother and grandfather, and were all Belgian nationals.
The airport was closed immediately after the crash which happened just before 1000 CET (0900 GMT). Several flights were cancelled with another handful of flights delayed at the start of the Belgian school half-term holidays.
Charleroi was due to re-open later on Saturday. "Our priority is dealing with this drama. Flights are being diverted to Liege and Brussels," Milioto said.
Charleroi airport, also known as Brussels South Charleroi serves as the country's second international airport after Brussels, Zaventem airport and expects to handle 140 000 passengers over the half-term holiday period.
Ryanair, which is the heaviest user of the airport, was not immediately available for comment.