An Italian court has sentenced a 90-year-old former Nazi corporal to life in prison over a wartime massacre portrayed in the novel and film Captain Corelli's Mandolin.

Rome's martial court found Alfred Stork guilty of the killing of at least 117 Italian military officers, who were executed by firing squad on the Greek island of Cephalonia in 1943, after they had surrendered.

Stork, who had confessed to playing a key role in the brutal execution to German prosecutors in 2005, was not in court.

"He didn't have the fortitude to stick to his admission of guilt and preferred to stay in the comfort of his German home," military prosecutor Marco De Paolis told the court.

Stork currently lives in Kippenheim, southwestern Germany.

On 8 September 1943 Italy, which had entered World War II under the leadership of Fascist dictator Benito Mussolini as an ally to Nazi Germany, switched sides after surrendering to the US and its allies.

The armistice sparked chaotic scenes, as Italians troops fighting across Europe alongside Nazis had now to fight against them.

More than 500,000 Italian soldiers were taken prisoner and at least 5,000 shot dead in the following weeks.

Italian troops in Cephalonia, a small island in the Ionian Sea, surrendered to the Germans after a week of fighting.

"We were told to kill them because they had been designated as traitors," Stork reportedly told German detectives.

"We piled up the bodies one over the other. Then we searched them taking their watches. In their pockets we found photos of their families, women and children," Stork confessed to German detectives.

The confession could not be used in Rome's trial because there was no defence lawyer present when it was recorded.

Historians put the total number of Italians killed in fighting or executed after surrender in Cephalonia somewhere between 1,700 and 9,400.

Rome judges said Stork personally took part in the execution of at least 117.

The massacre forms the backdrop to the bestselling 1994 novel Captain Corelli's Mandolin by British author Louis de Bernières, which inspired a 2001 movie starring Nicholas Cage and Penelope Cruz.

The sentencing came as Italy faces controversy sparked by the death of Nazi war criminal Erich Priebke.

Nicolas Cage
Hollywood star Nicolas Cage and Italian actor Francesco Cabras during the filming of Captain Corelli\'s Mandolin in Cephalonia (Reuters)