Italian police said they launched a pre-dawn swoop today to arrest 100 people suspected of trying to rebuild the top ranks of the Sicilian Mafia, which has been weakened by the recent arrests of powerful mob leaders.

The "Perseus" operation, conducted with more than 1,200 police officers, helicopters and anti-drugs units, was in progress across Sicily and parts of Tuscany.

The mobsters are being pursued on charges of extortion, trafficking arms and drugs and having mafia links.

They are suspected of trying to recreate the top-level Cosa Nostra body responsible for taking important decisions, with the support of Matteo Messina Denaro, one of the most powerful godfathers on the run.

"If Cosa Nostra was on its knees after operation Gotha in June 2006, then with operation Perseus it has been prevented from getting up again," said Italy's anti-mafia prosecutor Pietro Grasso.

Italian police have inflicted major blows on the Sicilian mafia with arrests of several high-profile mafiosi in recent years such as the "boss of bosses" Bernardo Provenzano in 2006 and his heir apparent Salvatore Lo Piccolo in 2007.

Young Sicilians have also been leading efforts to rally local business people into resisting payment of the "pizzo" or protection money that helps fund the Mafia's activities.