The explosion occurred on the road between Bandiagara and Goundaka in the Mopti area, early Thursday afternoon, a security source said. The region is known as a hotbed for jihadist violence.
Initially, police and local sources gave a provisional toll of 10 dead and many seriously injured.
"We have just transferred nine bodies to the clinic. And it's not over yet," said Moussa Housseyni of the local Bandiagara Youth Association.
Mines and improvised explosive devices (IEDs) are among the jihadists' weapons of choice. They can explode on impact or be detonated remotely.
A report by MINUSMA, the UN mission in Mali, found that mines and IEDs had caused 72 deaths in 2022 as of August 31. Most of the victims were soldiers -- but more than a quarter were civilians, it said.
Last year, 103 people were killed and 297 injured by IEDs and mines.