A mid-air collision between two helicopters has killed 13 French soldiers fighting against militants in Mali, French President Emmanuel Macron said on Tuesday.
Macron expressed “deep sadness” at the news of the Monday evening crash, which took place during a combat operation.
In a written statement, he expressed his support for the French military and stressed the “courage of the French soldiers”.
The statement provided no further details about the accident.
French Defence Minister Florence Parly said an investigation has been opened to determine the exact circumstances of the accident.
The operation in West and Central Africa involves 4,500 personnel and is France's largest overseas military mission.
A new surge in militant attacks in Mali has killed well over 100 local troops in the past two months, with the Daesh group often claiming responsibility.
The US has said West Africa's Sahel region is an emerging front in the fight against Daesh and other militant groups, including those linked to al Qaeda.
Before his death this year, Daesh leader Abu Bakr al Baghdadi congratulated "brothers" in Mali and neighbouring Burkina Faso for pledging allegiance.
France's Barkhane military operation is one of a number of efforts against the growing insurgency threat including a five-nation regional counterterror force and a UN peacekeeping mission in Mali.