Iran's Islamic Revolution Guards Corps (IRGC) claim to have shot down a US spy drone over Iranian airspace.
State media reported the military hit a drone, which they named as a RQ-4 Global Hawk, near Kuhmobarak in Iran's southern Hormozgan province.
The US military has not confirmed or denied the reports.
It comes days after the Pentagon said it was deploying 1,000 extra troops to the region in response to "hostile behaviour" by Iranian forces.
Washington has accused Iran of attacking oil tankers with mines in the Gulf of Oman, reports the BBC.
Tensions were further fuelled on Monday when Iran said its stockpile of low-enriched uranium would next week exceed limits it agreed with international powers in 2015.
Iran stepped up its production in response to tightening economic sanctions from the US, who left the landmark nuclear deal last year.
Kuhmobarak, where Iran says it shot down the drone on Thursday, is close to the Strait of Hormuz - a key route for global oil supplies.
The US military has not commented directly on the drone claim, but a spokesman for US Central Command told the Associated Press agency that there was no US drone over Iranian territory.