The submarine was to approach the Army naval exercise zone in the North Indian Ocean, Mehr News Agency (MNA) reported on Thursday.
The foreign vessel was spotted by anti-submarine helicopters but left the area immediately after learning of its identification,according to the public relations office of the Iranian Army statement.
Earlier in the day, Iran’s Army naval units successfully hit their targets by firing various types of cruise missiles and torpedo in the second day of the military drills.
The two-day 'Eqtedar-e Daryayi 99' naval drills kicked off on Wednesday in a vast area spanning the southern Makran coastal strip on the Sea of Oman and north of the Indian Ocean.
Iran’s naval forces are on full alert and in complete control of the Persian Gulf waters and the Sea of Oman against any external provocations, the commander of the Islamic Revolutionary Guards Corps Navy said earlier this week.
Speaking during the fifth anniversary of the arrest of American forces trespassing on the Iranian territorial waters, Rear Admiral Ali Reza Tangsiri stressed, “Any attempt to invade our land, water and air will be met with a rapid response.”
Two US Navy crafts, carrying 10 Marines, reached three miles into the waters surrounding Farsi Island in the Persian Gulf on January 12, 2016, because of what has later been announced as technical problems with the navigation systems of the US vessels.
They were released a day later after related examinations had made it clear the trespassing occurred unintentionally and the t the entry by the American Navy crafts apologized.