Four Iranian patrol boats from its Revolutionary Guard intercepted the U.S.-flagged container ship M/V Maersk Kensington last Friday in the Persian Gulf near the Strait of Hormuz in an internationally recognized maritime route, a Pentagon official told Fox News Tuesday.   

The news came as Iranian Navy vessels fired shots at and boarded a Marshall Islands-flagged commercial container ship in the Strait of Hormuz Tuesday, a senior defense official told Fox News.

The Iranian patrol boats encircled Maersk Kensington, but eventually withdrew without firing any warning shots or boarding the vessel, according to the official. Maersk Kensington did not request assistance, and U.S. Navy ships were not present or involved, according to the official.  

Maersk Kensington’s master reported the incident to U.S. Naval Forces Central Command a short time after the incident.

Shortly after the incident, the U.S. Navy Central Command issued a “notice to Mariners” warning vessels operating in the Gulf to be on the lookout for those Iranian patrol boats, according to a Navy official.

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The official would not speculate if the intercept was a test run for Tuesday’s operation involving Iranian patrol boats firing warning shots and boarding the Marshall Islands-flagged ship.  

The Maersk Tigris ship, originally heading to Jebel Ali in the United Arab Emirates, is now being escorted by the Iranian Navy into waters near Bandar Abbas, home of Iran’s largest Navy base.

The USS Farragut, a guided missile destroyer, is making “best speed” en route to the area and has dispatched a helicopter to get a closer look, the official said.

Col. Steve Warren, a Pentagon spokesman, said the cargo ship's master had initially refused an Iranian order to move further into Iranian waters, but after the warning shots were fired the Maersk Tigris complied.

The cargo ship, which had more than 30 people aboard, was directed to waters near Larak Island, he said.

The Iranian vessels, numbering five or six, were with the Iranian Revolutionary Guard Corps Navy, Warren said.

"It is inappropriate" for the Iranians to have fired warning shots across the ship's bridge in those circumstances, Warren said, adding that it was too early to know whether the Iranian intervention amounted to a violation of the freedom of navigation through a waterway heavily used by international shipping.

The spokesman said the U.S. government has "certain obligations" to defend the interests of the Marshall Islands, but he was uncertain how those obligations apply in this situation.

Warren said no one has been injured and no Americans are involved. The cargo ship issued a distress call and U.S. Naval Forces Central Command, based in the area.

A Maersk spokesman told Fox News that although Maersk, a Danish company based in Copenhagen, owns the vessel, it had “chartered” the ship to Rickmers Ship Management based in Hamburg, Germany. Maersk said it had no information about the crew or the cargo

The incident began at about 4:05 a.m. U.S. Eastern Daylight Time, Warren said.

Fox News’ Lucas Tomlinson, Catherine Herridge and The Associated Press contributed to this report.