Niger's defense ministry says three gendarmes were killed and four security forces injured in separate attacks this week.

In a statement Thursday night, the ministry said unidentified gunmen in a pick-up truck and on motorbikes struck gendarmes Wednesday night near the country's western border shared with Mali and Burkina Faso. One officer was injured.

Earlier Wednesday night, suspected Boko Haram militants hit near the town of Bosso in a region that has come under regular attack by the Nigeria-based extremists. Three security forces were injured while five assailants wearing explosive belts — three of them women — were killed.

Niger plans to close its borders for a presidential runoff vote scheduled for Sunday. President Mahamadou Issoufou is running for a second term.