A deliberate attack in southwestern Niger resulted in at least 44 civilian deaths and 13 injuries, including four critical cases, according to Interior Minister Mohamed Toumba.
The assault, attributed to Islamic State in the Greater Sahara* militants, targeted worshippers in a Fonbita mosque in Kokorou.
The ministry denounced the "cowardly and inhumane act" and promised intensified counter-terrorism measures.
The Nigerien government declared a 72-hour national mourning period starting Saturday for the victims. Flags will be flown at half-mast nationwide, and public events will be subdued.
*Daesh (also known as ISIS/ISIL/IS) is a terrorist organization outlawed in Russia and many other states