Iran has arrested 30 people on suspicion of spying for the United States, official media said.

"The Intelligence Ministry's active and pious forces, in their ardent confrontations with the agents of the CIA ... arrested 30 people who were spies for America," according to a state television.

The semi-official Fars news agency reported that the suspects had passed information to U.S. officials at embassies and consulates in third countries, including Malaysia, Turkey and the United Arab Emirates.

It said Iran had identified 42 U.S. intelligence officers in such countries, saying: "they engage in collection of information regarding Iran's nuclear, aerospace defense and bio-technology fields," among other areas of interest.