The US military said Wednesday it had blocked two attempts by the Iranian navy to seize commercial tankers in international waters off Oman, including one case in which the Iranians fired on the tanker.
Tehran has stepped up actions against tankers in the region since the United States tightened sanctions on Iran's own oil exports and other sections of its economy.
The Iranians sought to seize the Marshall Islands-flagged TRF Moss and hours later the Bahamian-flagged Richmond Voyager, in both cases fleeing after a US destroyer appeared on the scene, the US Central Command said in a statement.
It said that at 1:00 am Wednesday local time, one Iranian naval vessel approached the TRF Moss in the Gulf of Oman.
"The Iranian vessel departed the scene when US Navy guided-missile destroyer USS McFaul arrived on station," the statement said.
Around three hours later, the US Navy received a distress call from the Richmond Voyager, which was positioned more than 20 miles (32 kilometers) off the coast of Muscat, it said.
Another Iranian naval vessel was close to the tanker and messaged it to stop.
Before the arrival of the USS McFaul, "Iranian personnel fired multiple, long bursts from both small arms and crew-served weapons," Central Command said.
Several rounds hit the hull of the tanker but there were no casualties or significant damage, it said.
Central Command said that since 2021 Iran has "harassed, attacked or seized" nearly 20 internationally flagged merchant ships, "presenting a clear threat to regional maritime security and the global economy."
The tightened US sanctions, which aim to cut into Iran's export earnings, have led to the United States seizing Iranian-controlled tankers and shipments of crude to other countries.
But seizures come as the United States has sought to engage Tehran on some of the issues dividing them, the largest of which is restoring the 2015 agreement in which Iran accepted limitations on its nuclear program.
Most recently Oman initiated indirect talks between the two sides that were believed to focus largely on the release of Americans held by Iran.
In April Iran seized two tankers within a week in regional waters.
In one of the incidents, helicopter-borne Iranian navy commandos abseiled onto the deck of a Marshall Islands-flagged oil tanker, the Advantage Sweet, in the Gulf of Oman.
In 2019, Iran's Revolutionary Guards seized the British-flagged oil tanker Stena Impero in the Strait of Hormuz for allegedly ramming a fishing boat, and released it two months later.
In 2021, Iran released a South Korean oil tanker it had held for months amid a dispute over billions of dollars seized by Seoul.
And in May 2022, Iran seized two Greek tankers after a Russian-flagged tanker carrying Iranian crude was seized a month earlier near Athens. The two vessels were both released in November.