Iran says its navy warned US vessels to stop "provocative and aimless shooting".
Iran's Revolutionary Guard has rejected the US Navy's claim that fast-approaching Iranian speedboats in the Strait of Hormuz sparked a tense encounter in the already sensitive region.
The Guard's website, sepahnews.com, published a statement on Tuesday saying Americans were guilty of using "false narratives and unprofessional behaviour" and should more strictly "abide by international regulations."
Specifically, the statement said the Guard's navy warned the US vessels to stop their "provocative and aimless shooting."
A day earlier, the US said the Revolutionary Guard sent 13 armed speedboats too close to US Navy vessels in the Strait of Hormuz on Monday.
The Americans said its Coast Guard cutter fired warning shots when two of the Iranian boats came dangerously close.
The exchange comes as the United States and Iran engage in indirect talks in Vienna aimed at reviving the 2015 Iran nuclear deal, which the United States left in 2018.
Second similar incident in two weeks
Pentagon spokesman John Kirby declined to comment when asked about 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 to for," Kirby told reporters at the Pentagon.
"This activity is the kind of activity that could lead to somebody getting hurt and could lead to a real miscalculation in the region, and that doesn't serve anybody's interests."
It was the second time in two weeks that a US ship allegedly opened fire to warn vessels of Iran's paramilitary Revolutionary Guard.
On April 26, an American warship allegedly 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 maneuvered at high speed toward six Navy ships that were escorting the guided missile submarine USS Georgia through the Strait on Monday.
The sub was sailing on the surface.
The six Navy escort ships included the guided missile cruiser USS Monterey.
Iran regularly rejects the US Navy's claims with regard to similar incidents.
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