AFP reports that the militants on Thursday ambushed a column of civilian fighters from the Homeland Defence Volunteers (VDP), a group the government funds and trains to contain Islamist insurgents.
The government of Burkina Faso has declared a two-day mourning period as suspected militants killed at least 41 members of a government-backed civilian militia in the country's desert north.
AFP reports that the militants on Thursday ambushed a column of civilian fighters from the Homeland Defence Volunteers (VDP), a group the government funds and trains to contain Islamist insurgents.
According to the authorities, the attack was one of the heaviest single-day losses the civilian militia has experienced to date.
The attack also comes one month after an attack on a gendarmerie post killed 53 people - the worst strike on Burkinabe security forces in years.
"In this painful circumstance and as a tribute to the valiant VDP and civilians who fell in defence of the homeland, the President of Burkina Faso decrees a national mourning period of forty-eight hours, starting Sunday," government spokesman Alkassoum Maiga said in a statement.
Meanwhile, there have been a series of protests in recent months over the perceived failure of the government to curb a four-year Islamist insurgency that has killed thousands across Africa's Sahel Region and forced more than a million people to flee their homes.
Militants linked to al Qaeda and Islamic State have inflicted heavy casualties on the region's armies, killing soldiers in Burkina Faso, Niger and Mali almost every week in scattered attacks.
The Burkinabe army said about 100 militants were killed earlier this month in a joint offensive involving hundreds of troops from Burkina Faso and Niger, who also seized guns, improvised explosive devices and hundreds of motorcycles.