At least 40 civilians were killed in an attack on Sunday in Djibo, in northern Burkina Faso.
An army detachment in Djibo in northern Burkina Faso was the target of the attack, according to security sources.
A large number of militants attacked a military base, homes and internally displaced people's camps in the city Djibo, in the Sahel region, killing at least 40 civilians and injuring more than 42, the UN Human Rights Office (OHCHR) said Tuesday.
"Deliberately targeting civilians or individuals not taking direct part in hostilities constitutes a war crime," it added.
Since 2015, Burkina Faso has witnessed a cycle of violence at the hands of armed groups affiliated with ISIS and Al-Qaeda organisations, which are active in neighboring Mali and Niger.