The army in Mali says it has shot dead 16 people after their vehicle failed to stop at a checkpoint in the town of Diabali in the central Segou region.
At least some of the dead are believed to be Islamic preachers from the conservative Dawa sect and included Mauritanians as well as Malians.
They were travelling to a conference in the capital, Bamako.
Northern Mali is now controlled by Islamist militants, following a military coup in March.
Correspondents say the army may have mistaken the preachers for Islamist fighters.
The government said it was launching an investigation into the incident.
The Dawa sect originated in Pakistan and first spread to Mali in the 1990s.