The collision took place near Carces lake about 50 kilometres (30 miles) northwest of the resort of Saint-Tropez.

"The helicopters collided. There were three army personnel in one and two in the other. All are dead," police said in the nearby town of Brignoles, adding that one body had still to be recovered from the wreckage.

The Var region prefecture said the helicopters from the army's light aviation division were from a school based at Cannet-des-Maures.

Some 20 troops joined two rescue helicopters and a police chopper at the crash scene, along with local officials.

In a tweet Defence Minister Florence Parly expressed "great sadness" and said she was en route to the crash site.