An Iranian surface-to-air missile has shot down an American drone flying in international airspace over the Strait of Hormuz, a US official said.

Iran’s Revolutionary Guard said earlier that it had brought down a US drone amid heightened tensions between Tehran and Washington over its collapsing nuclear deal.

A spokesman said the drone was flying in Iranian airspace, contradicting the American official.

The reported downing of the RQ-4 Global Hawk comes after the US military previously alleged Iran fired a missile at another drone last week which responded to the attack on two oil tankers near the Gulf of Oman.

Hassan Rouhani
Iranian president Hassan Rouhani said his country is not seeking to wage war against any nation while at the same time stressing that it will withstand mounting US pressure (Iranian Presidential Office/AP)

The US blames Iran for the attack on the ships, which Tehran denies.

Iran’s paramilitary Revolutionary Guard, which answers only to supreme leader Ayatollah Ali Khamenei, said it shot down the drone on Thursday morning when it entered Iranian airspace near the Kouhmobarak district in southern Iran’s Hormozgan province.

Kouhmobarak is around 750 miles south-east of Tehran and close to the Strait of Hormuz.

Iran’s state-run IRNA news agency identified the drone as an RQ-4 Global Hawk.

A US official told the Associated Press that the Iranians had hit the drone with a surface-to-air missile. The official said the incident happened over the Strait of Hormuz in international airspace. The strait is the narrow mouth of the Persian Gulf through which 20% of all global oil moves through.

The attacks come against the backdrop of heightened tensions between the US and Iran following US president Donald Trump’s decision to withdraw from Tehran’s nuclear deal with world powers a year ago.

Iran recently has quadrupled its production of low-enriched uranium and threatened to boost its enrichment closer to weapons-grade levels, trying to pressure Europe for new terms to the 2015 deal.

In recent weeks, the US has sped an aircraft carrier to the Middle East and deployed additional troops to the tens of thousands already in the region.

Mysterious attacks also have targeted oil tankers as Iranian-allied Houthi rebels launched bomb-laden drones into Saudi Arabia.

All this has raised fears that a miscalculation or further rise in tensions could push the US and Iran into an open conflict, some 40 years after Tehran’s Islamic Revolution.