A statement said both Italians and Iranians had been arrested, including "some who are believed to belong to the Iranian secret services."
More details of the operation, dubbed "sniper," would be disclosed at a news conference later on Wednesday held by anti-terrorism prosecutor Armando Spataro.
Iran is subject to an international arms embargo and Italian Prime Minister Silvio Berlusconi has said on several occasions that trade sanctions against Tehran ought to be toughened up.
Spataro has spearheaded several high-profile cases in Italy, including attempts to have U.S. CIA agents tried on accusations of kidnapping a terrorism suspect.
