WASHINGTON (AP) — The Pentagon says an Iranian military plane fired upon, but did not hit, an unarmed U.S. drone aircraft a week ago in what a spokesman said was international airspace over the Persian Gulf.

Pentagon press secretary George Little disclosed the incident was disclosed Thursday.

Little said the drone aircraft was performing “routine surveillance” and was about 16 miles off the Iranian coast when an Iranian SU-25 warplane intercepted it and opened fire. He said it was the first time an unmanned U.S. aircraft was shot at in international airspace over the Gulf.

Little said the U.S. informed the Iranians that it would continue to conduct such surveillance flights in international airspace.