The Guardia di Finanza and Carabinieri police forces said they are accused of tax fraud and money laundering, through which they raised "substantial sums of money."
Some of the funds, plus offers collected from mosques, were "presumably destined to financing the activity of the radical Islamic organization al-Nusra [Front]," police forces said in a statement.
The money was also used to support imams living in Italy with radical views, including one who has been jailed for terrorism and another who has been expelled from Italy for his extremism, police said.
The main fundraiser was a Tunisian businessman living in Abruzzo who used his building renovation and carpet trading companies to create slush funds.
One of his methods was overpaying his employees, who would then be asked to return part of their wages in cash. This under-the-counter money would then be used illegally.
In a press conference, police officials said slush funds would first be sent to Germany, Britain or Belgium, before their final transfer, via couriers, to Turkey and Syria.
Saturday's operation also led to the seizure of assets worth 1 million euros (1.1 million dollars), including a couple of flats bought by some of the suspects.
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