A Frenchman sentenced to 20 years' jail in the Dominican Republic over a plot to smuggle a planeload of drugs has been transferred to France for health reasons, his lawyer said.

Alain Castany, one of four Frenchmen convicted in the so-called "Air Cocaine" case, arrived in France on Friday morning for medical treatment, lawyer Karim Beylouni told AFP.

Castany, 70, has been hospitalised after a motorcycle knocked him over while he was out on bail.

He will undergo surgery in France to try to avoid amputation of his leg, his Dominican lawyer Luz Diaz told AFP in Santo Domingo.

Castany and three other Frenchmen were arrested at the airport in the resort city of Punta Cana as their small Dassault Falcon 50 jet prepared to take off with what authorities say was a cargo of suitcases stuffed with some 700 kilograms (1,500 pounds) of cocaine.

Castany was convicted in 2015 of brokering the plot and was sentenced to 20 years in prison along with the two pilots and a passenger on the aircraft. His sentence was upheld in November last year.

The pilots, Pascal Fauret and Bruno Odos, managed to flee back to France. But they were re-arrested and are now under investigation by French authorities.

Last week the prosecutor's office in Marseille demanded that all four, along with seven other suspects in the case, be handed over to the court in Bouches-du-Rhone.

A French aviation security expert, Christophe Naudin, who is accused of helping the pilots escape in being held in a Dominican jail following his extradition from Egypt.

Source: AFP