Rome - Former "boss of bosses" Toto Riina, one of the most feared Godfathers in the history of the Sicilian Mafia, died early on Friday after battling cancer, Italian media reported.
Riina, who had been serving 26 life sentences and is thought to have ordered more than 150 murders, had been in a medically-induced coma after his health deteriorated following two operations.
The mobster, who turned 87 on Thursday, died in the prisoners' wing of a hospital in Parma in northern Italy just before 4am, according to the country's main dailies and ANSA news agency.
The hospital would not immediately confirm his death.
His wife and three of his four children had been given permission by Italy's health ministry Thursday for a rare visit to say goodbye.
Riina's eldest son Giovanni is serving a life sentence for four murders.
"You're not Toto Riina to me, you're just my dad. And I wish you happy birthday dad on this sad but important day, I love you," his other son Salvatore wrote on Facebook on Thursday.
An ageing Riina asked in July to be released from prison on the grounds of serious illness - a request that was denied after a court ruled the care he received behind bars was as good as he would get on the outside.
Doctors said at the time that the former boss was "lucid". He was caught on a wiretap earlier this year saying he "regrets nothing... They'll never break me, even if they give me 3,000 years" in jail.
Riina's most high-profile ordered hits were the assassinations in 1992 of anti-mafia judges Giovanni Falcone and Paolo Borsellino, who had worked fearlessly to bring more than 300 mobsters to trial in 1987.
He was also behind a series of bombings in Rome, Milan and Florence that killed 10 people.
"God have mercy on him, as we won't," said an association for victims of the Florence blast, according to the Fatto Quotidiano daily.
Salvatore "Toto" Riina, nicknamed "The Beast" because of his cruelty, lead a reign of terror for almost 20 years after taking control of the island's powerful organised crime group Cosa Nostra in the 1970s.
Riina, who was also dubbed "U Curtu" ("Shorty") due to his 5-foot-2-inch (1.58) height, for years denied all links to the crime group - nicknamed "the octopus" for its tentacled reach into all areas of society.
In 2009 he broke the Mafia code of 'omerta' - a vow of silence - and surprised those who thought he would take his secrets to the grave by admitting his link to the mob.
The son of a poor farmer, Riina was born on November 16, 1930 in Corleone, a vendetta-haunted village inland from Palermo and the birthplace of Don Corleone, the fictional Godfather in Francis Coppola's popular movie trilogy.
He is believed to have first murdered for the Mafia aged 19 and followed that a year later by killing a man during an argument - landing him behind bars for a six-year manslaughter stretch.
Once out, he became a foot soldier for volatile and vain boss Luciano Leggio, eventually taking over from him at the end of the 1970s when the cigar-puffing fugitive was caught and jailed.
Riina went on the run himself in 1969, but continued to lead the Corleonesi clan from hiding, increasing his influence by bumping off rivals such as Filippo Marchese, a hitman who garroted his victims in a "room of death".
Riina would elude police efforts to snare him for almost a quarter of a century - without ever leaving Sicily - and took charge of Cosa Nostra's key businesses, from drug trafficking to kidnapping and racketeering.
His bloody victory in the Mafia War of the 1980s was to prove his undoing however, as mobsters from defeated rival families began turning state witness against him, and police tracked him to a house in Palermo.
But the violence did not end there: from behind bars Riina ordered the murder of a 13-year old boy who was kidnapped in a bid to stop his father from spilling Mafia secrets. He was strangled and his body dissolved in acid.
In revenge for Riina's arrest and a new anti-Mafia law that saw jailed mobsters kept in total isolation, the group launched a series of bombings in Rome, Milan and Florence that killed 10 people.
After years in which only his lawyers were allowed to visit him, an ageing and cancer-riddled Riina asked in July 2017 to be released from prison on the grounds of serious illness - a request that was denied.
On Thursday, days after he was placed into a medical coma by prison doctors, Italy's Health Minister Andrea Orlando signed a waiver allowing Riina's family to visit him and say their goodbyes.