"The helicopters collided. There were three crew 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 two army aviation service helicopters based at nearby Cannet-des-Maures collided near Carces lake about 50 kilometres (30 miles) northwest of Saint-Tropez.

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