The Judiciary Spokesman, Gholamhossein Esmaili, said two of the Australians had been detained while using a drone to take pictures and video of its military areas.
Esmaili explained that the other Australian was arrested for spying for another country, adding that the two cases were ready to be sent to the court.
He, however, did not elaborate further on the time of arrest and names of the detainees.
Earlier, the Australian Government said that three of its citizens had been arrested in Iran and its department of Foreign Affairs and Trade in Iran was trying to provide consular assistance to their families.
Edited by Yahaya Isah/Felix Ajide