Interior Minister Alkassoum Indatou attributed Sunday's attack in the Tillaberi region, near the border with Mali, to "armed bandits, aboard several motorcycles, who have not yet been identified."
He said in a statement that 13 of the victims were from the village of Foney Ganda and five from the village of Tizegorou.
Local officials have blamed a series of massacres of civilians since last year on Islamic State's affiliate in West Africa, which along with al Qaeda-linked militants has been responsible for spiralling violence across the Sahelian countries of Niger, Mali and Burkina Faso.