The helicopter landed in a courtyard of the prison that had no protective netting overhead.

The three inmates - who are described as "dangerous" - jumped aboard and it took off before guards had time to react, prison officials and local police said.

"The whole thing was over in a flash," a prison guard said.

Getaway car waiting

The helicopter landed some 60 kilometres (37 miles) from the jail near the village of Auribeau-sur-Siagne, where the pilot was released and a getaway car was waiting.

After the escape prison officials immediately dispatched search teams around the region.

The convicts have been identified as Emile Forma-Sari and Jean-Philippe Lecase - both of whom are Corsican - and Abdelhamid Carnous, whose nationality was not immediately known.

All three were convicted of armed robberies and other crimes and one of the men was serving a sentence until 2012, police said.