DUBAI — Iran's elite Revolutionary Guards said on Thursday that the downing of a US drone near the Strait of Hormuz carried a "clear message" to the United States.

"The downing of the American drone was a clear message to America ... our borders are Iran's red line and we will react strongly against any aggression ... Iran is not seeking war with any country, but we are fully prepared to defend Iran," said the Guards' commander-in-chief, Hossein Salami, TV reported.

There was no immediate reaction from the United States.

The US-made Global Hawk surveillance drone was hit with a missile "after violating Iranian air space" over the waters of Hormozgan province, the Guard said in a statement.

The Iranian military did not immediately publish images of the drone. The incident comes at a time of growing antagonism between Iran and the United States following two waves of attacks on Gulf shipping believed to have been carried out with the Iranian support.

Tensions have been running high between Iran and the United States ever since President Donald Trump abandoned a landmark 2015 nuclear agreement in May last year.

The subsequent re-imposition of crippling unilateral sanctions has dealt a heavy blow to Iran's already flagging economy.

Washington has also bolstered its military presence in the Middle East in a campaign of "maximum pressure" campaign against Tehran.

Its deployment to the Gulf of an aircraft carrier task force as well as B-52 bombers, an amphibious assault ship and a missile defense battery has sparked fears of fresh conflict in the region.

One of the two tankers attacked in the Gulf of Oman last week was damaged by a limpet mine, the US military said Wednesday.

Commander Sean Kido of US Naval Forces Central Command, or NAVCENT, said the mine used in the attack "is distinguishable and it is also strikingly bearing a resemblance to Iranian mines that have already been publicly displayed in Iranian military parades".

The Japanese-owned Kokuka Courageous, loaded with highly flammable methanol, came under attack last Thursday as it passed through the Gulf of Oman along with the Norwegian-operated Front Altair.

It was the second attack in around a month on ships in the strategic shipping lane.

On May 12, two Saudi oil tankers and two other ships were damaged in mysterious "sabotage attacks" in the Gulf of Oman off the United Arab Emirates.

Kido told reporters in the UAE emirate of Fujairah that the US military had recovered "biometric information" of the assailants on the Kokuka Courageous including fingerprints.

This information "can be used to build a criminal case", Kido said as the US Navy took journalists to the damaged ship currently anchored some 14 km off Fujairah.

Washington has released images and a grainy video it says shows Iranians on a patrol boat removing an unexploded limpit mine attached to the Kokuka Courageous.

The US commander Kido said there was an "ongoing joint and combined investigation with our regional partners into the attacks" on the two tankers. — Agencies