US ship fires warning shots after 'unsafe' encounter with armed Iranian speedboats

An Iranian Islamic Revolutionary Guard fast in-shore attack craft approaches US naval vessels in the Strait of Hormuz. Photo / US Navy via AP

A group of 13 armed speedboats of Iran's Revolutionary Guard made "unsafe and unprofessional" high-speed manoeuvres toward US Navy vessels in the Strait of Hormuz today, and a US Coast Guard cutter fired warning shots when two of the Iranian boats came dangerously close, US officials say.

It was the second time in two weeks that a US ship opened fire to warn vessels of Iran's paramilitary Revolutionary Guard. The encounters come as the United States and Iran are in indirect talks in Vienna aimed at reviving the 2015 Iran nuclear deal, which the US left in 2018.

Asked whether it appeared the Revolutionary Guard are trying to pick a fight with the US Navy, Pentagon press secretary John Kirby declined to comment on the Iranians' intentions.

"Sadly, harassment by the IRGC Navy is not a new phenomenon. It is something that all of our commanding officers and the crews of our vessels are trained for," Kirby told reporters at the Pentagon.

"This is the kind of activity that could lead to somebody getting hurt and could lead to a real miscalculation there in the region, and that doesn't serve anybody's interests."

On April 26, an American warship fired warning shots when vessels of Iran's Revolutionary Guard came too close to a patrol in the Persian Gulf. That was the first such shooting in nearly four years. The Navy released black-and-white footage of that encounter in international waters of the northern reaches of the Persian Gulf near Kuwait, Iran, Iraq and Saudi Arabia.

In the latest incident, Kirby said, 13 Iranian vessels manoeuvred at high speed toward six Navy ships that were escorting the guided missile submarine USS Georgia through the Strait on Monday (Tuesday NZT). The sub was sailing on the surface. The six Navy escort ships included the guided missile cruiser USS Monterey.

A day earlier, the Monterey had intercepted an arms shipment aboard a dhow in the Arabian Sea apparently headed for Yemen, whose Houthi rebels are supported by Iran.

"They were acting very aggressively," Kirby said of the Iranian boats.

At one point, two of the Iranian boats broke away from the others and positioned themselves on the other side of the US ship formation. The two then sped toward some of the US ships.

In an attempt to de-escalate the situation, US crews issued multiple warnings to both groups of Iranian boats, including repeated bridge-to-bridge verbal warnings, said Navy Commander Rebecca Rebarich, a Navy 5th Fleet spokesperson.

After the two Iranian boats failed to respond to the multiple warnings and closed to within 275 metres, the Coast Guard cutter Maui fired a volley of warning shots from its .50-calibre machine gun. It fired another volley when the Iranian boats got within 137m.

The two Iranian boats then "altered course and increased their distance from the US forces", Rebarich said.