PALERMO, Sicily (Reuters) - Italian police issued arrest warrants on Monday (Nov 2) for mafia suspects after 32 shopkeepers and businessmen turned against the mob and denounced rackets in their neighbourhood.

Italian media said the large number of businesses willing to denounce the mafia in one of its traditional Sicilian strongholds was unprecedented.

Police said they had issued 22 arrest warrants for both mafia chiefs and their henchmen. A number of them were already behind bars and there was no immediate information on how many were still on the run.

"The investigation ... shows the suffocating pressure of extortion exercised by the most feared mafia chiefs, who, from 2003 to 2013, took charge of the top ranks of the mafia organisation," the police statement said.

Police said that after years of silence, businessmen in the Bagheria neighbourhood near Palermo "had found the courage" to provide details about mafia activities that had delved into everything from construction to fish sales.

"We have never seen such a large number of victims cooperate," police colonel Salvatore Altavilla was quoted as saying on the website of newspaper la Repubblica.

The Sicilian mafia, known as Cosa Nostra, was once Italy's most powerful criminal group but has lost some of its sway due to the state's ability to capture many of its top bosses.

Part of the police success has been tied to its ability to chip away at the mafia's code of silence, known as omerta, with the relatives of mafiosi and local businesses appearing to be increasingly willing to talk to authorities.