The French government called it a terrorist attack, though no group has yet claimed responsibility.
Unknown guns attacked the group Aug. 9 in the Kouré region, about 50 miles (50 km) from the capital Niamey.
French President Emmanuel Macron spoke with Nigerian President M. Mahamadou Issoufou about the incident, the French call “the deadly attack that frighteningly targeted a group of humanitarian workers”, according to a statement from the French Presidency on Monday.
The Elysee statement said President Macron had also sent condolences and country support to the families of the victims and that both the French and Nigerian presidents were working to clarify the circumstances of the attack.
“Their determination to pursue the fight against terrorists in the Sahel remains intact,” the statement said.
ACTED said aid workers helping people affected by the conflict should not be the target of attacks.
“This heinous crime should not go unpunished, nor will it distract us from our commitment to support the people of Niger,” the charity said in a statement.