Al-Alam Arabic language satellite channel, quoting a military source, said the drone was shot down "a few hours ago."
Fars news agency said the drone had violated Iran's airspace at its eastern borders. Fars has close ties to the Revolutionary Guards, an elite force in charge of the country's air defence and missile programmes.
"Our air defence and electronic warfare units managed to identify and shoot down an advanced unmanned spy aircraft -- RQ-170 -- after it briefly violated the eastern border territory," Fars said, quoting an unnamed military source.
The drone "was downed with slight damage. It is now under the control of our forces," the source added, calling the incident "a blatant territorial violation."
The RQ-170 Sentinel is a reconnaissance drone whose existence was revealed in 2009 by specialised media, and later confirmed by the US Air Force in 2010.
In January, Iran announced that its forces had downed two US drones after they violated Iranian-controlled airspace. It later said it would put the aircraft on public display.
