At least 14 civilians, mostly students, died Saturday on the way back from a school break after their bus hit an explosive device in northwestern Burkina Faso, according to a local official.

At least four others were also injured in the explosion on the Tougan axis in the Boucle du Mouhoun region, according to regional communications director Moumoula Arsene Kayaba.

The ages of the students were not immediately known.

Saturday's attack comes after gendarmeries Friday killed at least a dozen gunmen who had attacked their units in Inata in the Soum province, according to a statement by Burkina Faso's armed forces. Arms, ammunition and other materials were seized in the retaliation by Burkina Faso, it said.

Terrorists have been increasing attacks and gaining ground in Burkina Faso's north and east, displacing at least half a million people last year because of the insecurity.

Gunmen have targeted Inata before, killing one gendarme in October, and six others in September.