Italy's Silvio Berlusconi is not being investigated in connection with a Mafia bomb attack in Florence in 1993, a court said after reports that he was being probed on the evidence of a mobster-turned-witness.

The Italian media has buzzed with reports that Berlusconi and an associate would be linked to the Mafia by a mob informant in open court on Friday Dec. 4. But he told a rally in Sardinia that such talk was "unfounded and insulting".

Right-wing daily Libero wrote that the conservative leader and a senator who has been convicted of association with the Cosa Nostra, Marcello Dell'Utri, were being investigated. A magistrate heading the case denied the report.

"What Libero says is not true," the chief prosecutor for the city of Florence, Giuseppe Quatrocchi, told reporters.

The Sicilian Mafia declared war on the state in the early 1990s with bomb attacks in Milan and Rome and on Florence's Uffizi Gallery, one of Italy's main cultural treasures.

Five people died in the Florence car-bombing, part of a Mafia campaign to scare the state into relaxing the harsh prison regime served by convicted mobsters.

Mafiosi were jailed for the bombings but a court probe into possible links with leading politicians and business figures was dropped in 1998 -- then reopened this year based on new evidence from a jailed mobster turned state witness, Gaspare Spatuzza.

Spatuzza has told magistrates, in evidence reported widely in the media and confirmed by court sources, that Berlusconi and Dell'Utri had been mentioned to him in connection with the attacks by one of the Mafia bosses now serving multiple life sentences.