ROME -- Dozens of "ultras" fans with AC Milan and Inter Milan soccer clubs were targeted in a major operation in Italy on Monday for alleged organized crime offenses, according to local authorities.

Some 19 people were arrested overall, and variously charged for allegedly being involved in organized crime offenses, including extortion and assault "aggravated by mafia methods," Milan prosecutors said.

Three people were put under house arrest, while the others were brought to jail.

The operation was ordered by Milan prosecutors in coordination with the local anti-mafia district directorate and carried out by the Italian financial police and central investigative force (Sisco).

Investigators explained both leaders of the extreme wings of Inter and Milan's fan clubs (the so-called ultras) were among those arrested and charged with criminal conspiracy.

"Taking advantage of their role inside the stadium, the suspects carried out a series of football-related crimes aimed at accumulating illicit profits," police said in a statement.

Addressing a press conference later in the day, Milan prosecutors explained the operation would confirm existing links between the ultras of Italian soccer clubs (not limited to Inter and Milan) and organized crime syndicates.

In this specific case, the Inter and Milan ultras would have built connections with 'Ndrangheta, the powerful mafia rooted in the southern Calabria region, and operating at the national and global level.

"Football clubs are to be considered as injured parties in this case, according to our reconstruction," Milan chief prosecutor Marcello Viola told the press conference.

Officially rivals, the ultras of the two football teams would in fact have struck a "non-belligerence deal" aimed at keeping their illicit activities quiet, the chief prosecutor also told La Stampa newspaper on the sidelines.

In a statement, AC Milan club declared they would be ready to cooperate fully with judiciary authorities in the following phases of the inquiry.