A lawyer for convicted Cosa Nostra "boss of bosses" Bernardo Provenzano says the man who reputedly led the Mafia's powerful Corleone clan has died, a decade after his capture in Sicily following decades of hiding in the countryside.

The lawyer, Rosalba Di Gregorio, said Provenzano died Wednesday. In recent years, Provenzano had been held under strict security measures at a Milan hospital.

Di Gregorio had cited Provenzano's increasing physical frailty and mental infirmity in several failed attempts to persuade anti-Mafia prosecutors to ease the rigid prison conditions intended to prevent mobsters from wielding power from behind bars.

The reputed Cosa Nostra "capo dei capi" (top boss) was arrested in 2006 after 43 years as a fugitive. He had been convicted in absentia of ordering or carrying out multiple murders.