France's anti-terror prosecutor's office said Monday it would probe the killing of eight people, including French aid workers, by gunmen in Niger.
It would investigate charges of "assassinations with links to a terrorist enterprise" and "criminal terrorist association", the office said in a statement.
France and Niger remain determined to pursue their fight against terrorist groups operating in the West African Sahel region, French Foreign Minister Jean-Yves Le Drian said on Monday.
Le Drian said France would mobilize all means necessary to shed light on Sunday's attack, which killed six French aid workers.
"Our two countries remain determined to continue our joint battle against the terrorist groups in the Sahel," he said.
French humanitarian aid group ACTED said seven of its colleagues, along with one of its guides, had been killed in the gun attack in Niger on Sunday.
"It is with profound grief that we confirm the death of seven of our colleagues as well as their guide in Niger who were senselessly and cowardly murdered by armed individuals in the Kouré area, southeast of Niamey, on August 9th 2020," ACTED said in a statement released on Monday.
Gunmen on motorcycles killed the six French aid workers, a Nigerien guide and a driver in a wildlife park, officials said.
The group was attacked in a giraffe reserve just 65 km from the West African country's capital Niamey, the governor of Tillaberi region, Tidjani Ibrahim Katiella, told Reuters. "They were intercepted and killed," he said.