One of Italy's most notorious mafia bosses, Francesco "Sandokan" Schiavone, has turned state's witness after 26 years behind bars, a judicial source confirmed to AFP Friday.

Schiavone, who led a Camorra clan in Casal di Principe near Naples, was once considered one of Europe's richest and cruellest criminals.

He was arrested in a bunker in his hometown while on the run in 1998.

Schiavone has been serving several life sentences -- including for multiple murders -- since being convicted in the landmark "Spartacus" maxi-trial against 36 Casalesi clan members.

He was convicted in 2005 with his final appeal being dismissed in 2010.

Chiara Colosimo, the head of parliament's anti-mafia commission, hailed his decision to cooperate with authorities as "another hard blow against the Camorra and organized crime".

Schiavone and his crew were involved in brutal score-settling between clans fighting for control of Casal di Principe in the 1980s and 90s as well as peddling illegal drugs.

Their cruelty and economic and political power were exposed in Robert Saviano's best-selling book, "Gomorrah", later made into a film and TV series. Saviano was forced into hiding and is still under police protection.

In an Instagram post on Friday, Saviano said he would wait and see what kind of information the mobster would provide before hailing his decision to turn.

"Will he be able to do it without revealing where the Camorra's money is and without demonstrating real political and business connections?" Saviano wrote.

  Prison transfer 

 Several of the mobster's family have already collaborated.

His cousin, Carmine Schiavone, turned state's witness in 1993, revealing notably how the mafia dumped toxic waste in fields, wells, and lakes -- activities blamed for a spike in cancers in the local population.

Two of his sons, Nicola -- thought to have succeeded him, before being arrested in 2010 -- and Walter, turned "pentito" in 2018 and 2021, respectively.

Schiavone had been recently transferred from prison in northern Italy to a facility in L'Aquila, where Sicilian Mafia boss Matteo Messina Denaro was cared for before his death last year.

Schiavone was said to be ill, but some media reports Friday suggested the rumours were a ruse to disguise a transfer driven by his collaboration.

Schiavone was called "Sandokan" for his apparent resemblance to the actor who played the pirate hero of that name in a popular 1970s TV series -- a moniker that only added to the legend surrounding him.