Iranian TV and other media say an American drone aircraft has been captured after entering the country's airspace.
They say the unmanned ScanEagle aircraft was gathering information over the Persian Gulf when it strayed into Iranian territory. It is said to have been captured by a Revolutionary Guards naval unit sometime in the last few days but gave no details about how it happened.
However the US navy has denied losing any drones over the Gulf recently.
In November Iran complained to the UN that repeated US violations of its airspace were "illegal and provocative acts".
Last year Tehran claimed it captured a CIA spy drone after it entered Iranian airspace from its eastern borders with Aghanistan and Pakistan.
The Americans initially said it had become lost before admitting the drone had been monitoring Iranian military and nuclear facilities.
Tehran has claimed it captured a US spy drone in the Persian Gulf after the unmanned aircraft entered Iranian airspace, Iran's Press TV reported. The US Navy denied the claim, saying that none of its drones in the Gulf region were lost.
The US Navy says all of its drone unmanned aircraft are accounted for. Iran claims it captured one drone. Iranian State TV showed pictures of what was said to be the drone. (Dec. 4)
Iran's Islamic Revolution Guards Corps (IRGC) has captured a US ScanEagle drone over the Persian Gulf waters upon its intrusion into the Iranian airspace.
IRGC Navy Commander Rear Admiral Ali Fadavi made the announcement on Tuesday, adding that the Iranian armed forces enjoy full intelligence command over foreign movements in the Persian Gulf region.
Referring to the captured ScanEagle drone, the Iranian commander pointed out, "Such drones are usually launched from large aircraft carriers."
The ScanEagle drone, which has a 10ft (3m) wingspan, is a long-endurance aircraft built by Insitu, a subsidiary of Boeing.Iran has released footage of the captured drone.