Suspected militants killed four soldiers in Burkina Faso's northern Loroum province on Sunday, the army said, in the latest of a wave of attacks.
The assault came a day after protesters massed in the capital Ouagadougou, accusing the government of failing to stop the mounting violence
Groups linked to al Qaeda and Islamic State have waged a four-year insurgency in the desert north, killing thousands of people and displacing a million.
Anger has been mounting for the last two weeks, since 53 people were killed on Nov. 14 in the worst attack on security forces in years. Since then, at least 26 more soldiers and civilians have been killed in scattered attacks in the West African country.