A convicted killer who had already made one helicopter-assisted prison break and organized another, has escaped by helicopter from a French prison for a second time.

Pascal Payet, 43, broke out of Grasse prison, southeast France, on July 14 after a helicopter hijacked by four masked men landed on the roof of one of the prison buildings, said a source close to the investigation.

The helicopter, which had been hijacked earlier in the night at the Cannes-Mandelieu airport, landed some time later at Brignoles, 38 kilometers northeast of Toulon, on the Mediterranean coast.

Payet and his accomplices released the pilot unharmed and fled the scene.

Payet, who is from the southern French city of Marseille, is a career criminal with a long record of violent crimes.

He was jailed for a 1988 armed robbery and was eventually convicted of murder after killing a guard during a security van robbery in 1997.

July 14's escape was the second time he had broken out of a French jail in such spectacular fashion.

In October 2001, he escaped with another inmate in a helicopter from Luynes prison in southeast France.

Payet had been awaiting trial for the murder committed during the 1997 robbery, when he shot the security guard 14 times with a Kalashnikov automatic rifle.

The other prisoner who escaped, a convicted murderer, was recaptured only six days after the 2001 break-out, but Payet remained on the run for several years.

Still at large in 2003, Payet helped three other inmates break out of Luynes, the same prison from which he had escaped. Again a helicopter was used in the escape - and again the other three prisoners were arrested within weeks.

Payet was himself eventually recaptured, and in January this year was sentenced to seven years for having organized the 2003 break-out. He got a six-year sentence for his own 2001 escape.

In 2005, he was finally found guilty of the murder committed during the 1997 robbery and received a 30-year sentence, confirmed on appeal in 2006.

There have been at least a dozen helicopter break-outs in the past 20 years, although those involved have usually been recaptured.