Security sources in Burkina Faso say jihadist insurgents have killed 14 people, including four soldiers, near the northern city of Kaya.
The attack coincided with a visit by interim leader Captain Ibrahim Traoré.
It targeted a unit of soldiers and defence volunteers tasked with protecting repairs to water supply facilities in the town of Zorkoum.
The withdrawal of French forces from Burkina Faso and Mali, and their replacement by mercenaries from Russia's Wagner Group, has done little to turn the tide of jihadi violence.