Rome - A Mafia war was stopped in its infancy yesterday after the arrest in Sicily of 45 alleged gang members, including three men - a professional mobster, a doctor and a builder - who are said to have been in charge of Cosa Nostra since the arrest in April of the capo di capi Bernardo Provenzano.

Piero Grasso, the national anti-Mafia prosecutor, said after the arrests, "We can confirm that the Mafia organisation, at this moment, is on its knees."

Yesterday's multiple raids were brought forward after investigators learnt from wire taps that a new Mafia war was on the point of breaking out, after 13 years of relative peace.

According to Mr Grasso, one of the men arrested, Nino Rotolo, said to be a recidivist gangster, "was planning a series of murders to annihilate the family of Salvatore Lo Piccolo and become the undisputed boss of the clan in the city". Mr Lo Piccolo, is seen as one of the two possible successors to Provenzano, the clan's legendary leader.

Nobody was going so far as to suggest the Mafia was finished - its grip on Sicily is too firm and it is too well entrenched to be defeated by the loss of a few men at the top - but if Mr Grasso's claim is right, Cosa Nostra has been decapitated twice within three months, which will put a severe strain on the mob's ability to regroup.

The three men alleged to be at the top of the organisation were named as Nino Rotolo, Antonio Cina, the doctor who treated Provenzano, and Francesco Bonura, a builder. The arrests were the culmination of years of patient police work rare in the often dubious annals of the Italian state's fight against the Mafia.

The hunt for Provenzano, who had not been seen by the police since 1963, had been under way for 10 years, and began picking up speed last year as more and more of the messengers used to deliver the "pizzini", hand-typed notes, by which Provenzano kept in touch with his underlings, were identified and arrested.

A breakthrough came when DNA samples of Provenzano were obtained from a hospital in Marseilles to which he had travelled secretly with his wife in 2003 for a prostate operation.

The pressure was building, to the extent that in March the Provenzano family's lawyer said Provenzano "has been dead for years". The claim was greeted with shock and disbelief: there had been no rumours that the gang boss was in poor health. But once he was actually arrested, on the day that Silvio Berlusconi lost the general election, the lawyer's words were interpreted as meaning that the gangster was finished.

In a dilapidated shack outside Corleone where Provenzano had been hiding for months if not years, police found messages from the gangster's correspondents. Many were in code, but Mr Grasso claims police have cracked it, and the intelligence in the notes led them to yesterday's raids.

Mr Grasso and his team claimed that the "triumvirate" in charge of the Mafia held meetings in a steel-lined garage in Palermo, sitting on plastic chairs around a table, with no telephones or other electronic equipment present (though the police managed to install a spy camera).

As well as the three men alleged to be at the apex of Cosa Nostra, Mr Grasso said that the "regents" of 13 Mafia families in six districts had been arrested in yesterday's raids.

Among other acts of extortion and intimidation, police learnt of attempts by the mob to frighten Chinese shopkeepers around Palermo's railway station into paying protection money, by putting glue in the locks of their shop shutters - a traditional Mafia warning.

"It's a good day for Parliament," Italy's Interior Minister, Giuliano Amato, said. "The struggle against the Mafia remains a priority for our country."