Italian police said Tuesday they had arrested 13 people suspected of helping a top Mafia fugitive hide, communicate with other mobsters and conduct his business.

Investigators said that with Tuesday's arrests they are closing in on Matteo Messina Denaro, a fugitive who is among a handful of mobsters vying to take over the Sicilian Mafia. Most of the arrests were carried out in Trapani, a city in Western Sicily that is the power base of Messina Denaro.

"He's the last of the great fugitives," said Giuseppe Linares, the top police official in Trapani. "This operation strikes at his breeding ground and allows us to understand the essential structure" protecting him.

Police said the suspects aided Messina Denaro by providing fake documents and money, as well as conducting business on his behalf. The documents allowed Messina Denaro to come out of his hideout and travel abroad, investigators say, including in Venezuela for his business in drug trafficking.

The suspects also allegedly helped Messina Denaro keep contact with other Mafia bosses, including the now-jailed top mobster Bernardo Provenzano. They carried "pizzini," or encrypted notes, to and from the bosses.

Messina Denaro has been trying to impose his power in Palermo, the Sicilian capital, and become the new head of the Sicilian Mafia, weakened by the arrest of Provenzano in April 2006.

While some of his main competitors for the job, such as boss Salvatore Lo Piccolo, have been apprehended, Messina Denaro remains at large. Linares said that until Tuesday's operation, no arrests had been made in his close circle in over a decade.

Those arrested include businessmen in Trapani as well as at least one suspect in Rome, who provided the fake documents, said Linares. Charges included criminal association, extortion and drug trafficking.

As part of the raids, police searched the cells of some 40 inmates across Italy. Many of them will be moved to other prisons, as part of police efforts to cut transfers of money and communication between them and Messina Denaro.