Italian police have arrested alleged supporters of the elusive head of the Sicilian mafia, uncovering a secret network of messages that allowed the fugitive boss to give orders to his mobster allies.

Police said in a statement that their "Year Zero" operation, which led to 22 arrests in towns near the Sicilian city of Trapani where Matteo Messina Denaro's criminal empire is based, allowed them to uncover a system of paper notes, or "pizzini", that he uses to communicate to his underlings.

Denaro is believed to be the head of Cosa Nostra, the Sicilian mafia.

"The operation is part of the larger investigative operation aimed at the capture of the fugitive Matteo Messina Denaro, also through the progressive weakening of his criminal networks and economic resources," the statement said.

The suspects have been charged with crimes including mafia association and extortion.

Police confirmed to AFP that those arrested are Denaro's closest allies, including brothers-in-law Gaspare Como and Rosario Allegra, who are alleged to manage the boss' most important affairs.

News agency AGI quotes wiretapped recordings of one of those arrested on Thursday praising the January 1996 murder and dissolving in acid of Giuseppe Di Matteo, the 14-year-old son of mafia turncoat Santino Di Matteo.