Salvatore Riina is believed to be responsible for more than 150 murders including assassinations of Italian judges
Notorious Sicilian mafia boss dies after two decades behind bars
One of the most feared bosses in the history of the Sicilian mafia died early on Friday after battling cancer, Italian media reported.
Salvatore "Toto" Riina, known as the "boss of bosses", had been serving 26 life sentences and is thought to have ordered more than 150 murders. He had been in a medically-induced coma after his health deteriorated following two operations.
The gangster, 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 on 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 son Salvatore wrote on Facebook on Thursday.
Riina was captured in Palermo, Sicily's capital, in 1993 and imprisoned under a law that requires strict security for top mobsters, including isolation in prison and limited time outside their cells.
He had 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 mafiosi 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.
The Italian bishops conference ruled out a public church funeral for the mass murderer. Pope Francis declared all mafiosi "excommunicated" from the Catholic Church in 2015.