The crash occurred at 8.30 on Friday morning between the towns of Cabasse and Carces in the Var department of southern France, 50 kilometres from Saint Tropez.
“The helicopters collided. There were three crew in one and two in the other. All are dead,” police in the nearby town of Brignoles told AFP, adding that one body had still to be recovered from the wreckage.
The Var region prefecture said two army aviation service helicopters based at the Army’s School of Light Aviation (EALAT) in nearby Cannet-des-Maures collided near Carces lake.
All the people on board were officers, a source close to the inquiry said.
“One of the helicopters broke up and crashed onto a road, the second crashed about 150 to 200 metres away and burned,” said Jean-Luc Videlaine, prefect of the Var region.
The local police prefecture of Var confirmed earlier that there were “several fatalities” and that it had set up an emergency crisis centre at the scene.
Some 20 troops joined two rescue helicopters and a police chopper at the crash scene, along with local officials.
Two police helicopters were still searching the crash scene shortly after midday, while rescue services had blocked access to a forest road near the lake, according to an AFP journalist.
In a tweet Defence Minister Florence Parly expressed “great sadness” and said she was en route to the crash site, while President Emmanuel Macron hailed the “commitment of these officers who were preparing themselves for future missions.”
'Solidarity' with family, comrades
The French-made Gazelle helicopters entered service in the 1970s, and are used for reconnaissance and light attacks as well as training.
A local councillor, Jean-Pierre Veran, said helicopters “regularly” fly over the zone and there had never been an accident, calling it a “terrible shock” with debris spread over a large area.
Army chief-of-staff Jean-Pierre Bosser expressed his “solidarity with thefamily and friends of the victims, as well as their comrades” at the training facility.
An investigation later determined it was caused by pilot error.