REUTERS - Italian police targeting historic mafia families arrested 95 people on Monday for extortion, drug trafficking and money laundering, and in the process they may also have solved the century-old mob murder of a New York detective.

After two years of investigations, the arrests went after members of two mafia groups that have long operated in the western part of Palermo, the island's capital and largest city, court documents showed.

"There hasn't been a dragnet on this scale in many years," finance police Colonel Calogero Scibetta told Reuters. "These arrests have wiped out two entire mob families."

In recent years police and prosecutors have dealt severe blows to the Sicilian mafia, historically Italy's most powerful criminal group, while its sister organisation, the 'Ndrangheta of Calabria at the southern end of the Italian mainland, has grown in strength by becoming a big importer of cocaine.

To a Sicilian mob decimated by arrests and seeking to rebuild, criminal pedigree is important, as the investigation demonstrated when it wiretapped a 2013 conversation between two suspected young mobsters talking in their car.

In the details of the conversation, which features in the 872-page arrest warrant published on Monday, one of the mobsters, Domenico Palazzotto, said his family had celebrated the 100-year anniversary of the 1909 murder of Italian-American New York policeman Lieutenant Giuseppe "Joe" Petrosino.

Petrosino had come to Sicily to investigate the mafia, then known as the "Black Hand" in New York, and was shot dead in a magnolia-shaded Palermo square near the port almost immediately after his arrival.

"We have been mobsters for 100 years," says Palazzotto, 33, according to a wiretap planted by police in his Audi A3.

"My father's uncle, whose name was Paolo Palazzotto ... was the first to kill a cop in Palermo ... Joe Petrosino, an American cop," he says.

Palazzotto shot Petrosino on behalf of his boss, Don Vito Cascio Ferro, the assassin's great-nephew said.

"The young mafiosi see the criminal acts of their ancestors as a badge of honour," Scibetta said.

On Saturday, Pope Francis shone a spotlight on the evils of Italian organised crime.

During a trip to Calabria he said the 'Ndrangheta was an example of the "adoration of evil and contempt of the common good" and said mafia members were excommunicated - totally cut off - from the Church.