They were falling asleep on a thin mat that they had been sharing since they were married five years ago. Suddenly, the roar of motorcycles woke them up. Armed men then dragged Rainatou Diallo and her husband, Adama Diallo, out of bed and into their courtyard.

Without a word, the men shot Mr. Diallo dead. As Ms. Diallo fled the village, one of many engulfed by violence in Burkina Faso, she recognized her husband’s masked killers: They were neighbors.

Burkina Faso, a nation that once prided itself on tolerance and peaceful interethnic relations, is now home to one of the deadliest conflicts in West Africa. Since the current military leader, Capt. Ibrahim Traoré, seized power in a coup in 2022, he has escalated a war against Islamist insurgents that has now killed tens of thousands of people and displaced nearly three million others.

To beef up the ranks of his embattled military, Captain Traoré’s government recruited tens of thousands of men into a civilian militia, known as the Volunteers for the Defense of the Homeland. The militia was created by a previous leader to protect communities against the insurgents. But under Captain Traoré, it has spread unchecked violence and pitted local populations against each other, with minority ethic groups being brutally targeted in what some analysts fear will lead to a civil war.

Acts of violence against local populations involving militiamen have more than doubled since Captain Traoré’s coup, according to data compiled by the Armed Conflict Location & Event Data Project. The militiamen have carried out executions, forced disappearances or looting every six days on average, the data shows.