BEIRUT (Reuters) – The Iranian Revolutionary Guards said on Saturday that U.S. Navy ships came close to their vessels in the Gulf and shot flares.

The USS Nimitz and an accompanying warship drew close to a rocket-bearing Iranian vessel on Friday and sent out a helicopter near a number of Guards vessels close to the Resalat oil and gas platform, the Guards said in a statement published by their official news site Sepah News.

“The Americans made a provocative and unprofessional move by issuing a warning and shooting flares at vessels …,” the statement said. “Islam’s warriors, without paying attention to this unconventional and unusual behaviour from the American vessels, continued their mission in the area and the aircraft carrier and accompanying battleship left the area.”

A U.S. military statement said a U.S. Navy helicopter saw several IRGC vessels approaching U.S forces at a high rate of speed and deployed flares after it could not establish communications with the boats.

The statement said the interaction was “safe and professional.”

Last Tuesday, a U.S. Navy ship fired warning shots when an Iranian vessel in the Gulf came within 150 yards (137 metres) in the first such incident since President Donald Trump took office in January, U.S. officials said.

In a statement, U.S. Naval Forces Central Command said the patrol craft, named Thunderbolt, fired the warning shots in front of the Iranian vessel after it ignored radio calls, flares and the ship’s whistle.

The vessel belonged to the Revolutionary Guards, the statement said, adding that it stopped its unsafe approach after the warning shots were fired.

A U.S. official, speaking on the condition of anonymity, said the Iranian boat was armed but that the weapons were unmanned. The Thunderbolt was accompanied by a number of other vessels, including those from the U.S. Coast Guard.

Years of mutual animosity had eased when Washington lifted sanctions on Tehran last year as part of a deal to curb Iran’s nuclear ambitions. But serious differences remain over Iran’s ballistic missile programme and conflicts in Syria and Iraq.

The Trump administration, which has taken a hard line on Iran, recently declared that Iran was complying with its nuclear agreement with world powers, but warned that Tehran was not following the spirit of the accord and that Washington would look for ways to strengthen it.

During the presidential campaign last September, Trump vowed that any Iranian vessels that harass the U.S. Navy in the Gulf would be “shot out of the water”.