A Somali man has been jailed for life in Italy for raping, torturing and murdering migrants for pleasure in a desert camp he helped to run in Libya.

22-year-old Osman Matammud was found guilty of cruelty as he extorted money from migrants trying to reach Europe.

Matammud killed at least 13 people and not four as previously thought, the Milan court said on Friday.

Photos: Somali man jailed for life in Italy for brutal rape, torture and murder of at least 13 migrants in Libyan camp

Matammud raped dozens of women, some of them girls. His crimes could not be justified by "his traumatic experiences" as his lawyers had tried to argue, the court said.

Matammud was spotted by his victims at a migrant centre in Milan after travelling to Europe to claim asylum. He was saved from being lynched on the spot by Italian police.

"In a 40-year career I have never seen anything as horrific," said Ilda Boccassini, one of the judges, who has prosecuted notorious mafia murderers.

Seventeen of his Somali victims told the court that he had tortured them with electric shocks and metal rods, beaten them with stones and raped the women.