PALERMO, Italy (Reuters) - Police arrested the suspected new head of the Sicilian mafia and 45 other alleged gangsters on Tuesday, dealing a major blow to the mob as it tried to rebuild after years of setbacks.

Settimo Mineo, an 80-year-old jeweler with a previous mafia conviction, was elected to take the helm of the crime group Cosa Nostra, or “Our Thing”, at a secret meeting of mob families from in and around the Sicilian capital Palermo in May.

It was the first such gathering of the powerful Palermo clans since their previous leader, Salvatore “Toto” Riina, was arrested in 1993 and convicted of ordering dozens of murders.

Riina died in prison last year while serving 26 life sentences. Italian media have long speculated over who might have replaced him, but prosecutors said on Tuesday Palermo mobsters waited until after his death to anoint a successor.

“There has been a return to the old, archaic rules of ‘Cosa Nostra’,” chief prosecutor Francesco Lo Voi told reporters. “During the course of the (May) meeting ... they discussed the need to re-establish rules which had been lost on the street.”

Once all-powerful on Sicily, the world's most famous crime gang has been squeezed over the past two decades, with many bosses put behind bars, businesses sequestered and locals increasingly ready to defy it here.

Italian media showed pictures of the white-haired, bespectacled Mineo being led away by police, his handcuffed hands hidden beneath a coat.

“There is no more room for this type of scum in Italy,” Deputy Italian Prime Minister Luigi Di Maio wrote on Instagram after the wave of pre-dawn arrests.

ON THE RUN

The Palermo region has traditionally been the most powerful group within the Cosa Nostra cupola, or hierarchy, and police had been on the lookout for years for signs that it was trying to regroup and re-exert its authority.

“With an extraordinary operation in the Palermo province, the police have dismantled Cosa Nostra’s new ‘cupola’,” Interior Minister Matteo Salvini said on Twitter.

Mineo was sentenced to five years in jail for mafia-related crimes at the so-called “maxi-trial” that ran from 1986-1992 and was spearheaded by prosecutors Giovanni Falcone and Paolo Borsellino.

Both Falcone and Borsellino were murdered in 1992 on Riina’s orders after verdicts were delivered. Following their deaths, the state poured resources into the fight against the mob and ground down Cosa Nostra.

“If the (Palermo) group meets, it meets to decide serious things ... So we found ourselves facing danger and for that reason the police intervened rapidly,” Lo Voi said.

One prominent mafioso the police have been unable to capture is Matteo Messina Denaro, nicknamed “Diabolik”, who has been on the run since 1993 and comes from the province of Trapani, which lies to the west of Palermo.

Some media have said he was Riina’s natural heir, but Sicilian prosecutors have denied he is the boss of bosses, saying he never held sway over the powerful Palermo clans.

“He is one of Cosa Nostra’s most prestigious leaders, but he is from Castelvetrano, in the province of Trapani, and he does not command the Palermo group,” Salvatore De Luca, Palermo’s deputy prosecutor, said on Tuesday.