The guided-missile destroyer USS Nitze (DDG-94) was followed and harassed by four Iranian patrol boats on Tuesday in the Persian Gulf, defense officials confirmed to USNI News.

The destroyer was in the vicinity of the Strait of Hormuz when four Iranian Revolutionary Guard Corps Navy high-speed patrol boats came at the ship without responding to hails or warning flares fired from Nitze, according to a video of the incident provided to USNI News.

“This is USS Nitze reporting from the Southern Arabian Gulf,” said a voice on the video reporting the ship’s location and speed.

“We have visual contact with four Iranian… WPBs… Bridge to bridge COMMS were conducted but no response. Weapons uncovered… appears to be unsafe, unprofessional.”

While the voice is making the radio report, the four patrol boats speed in a serpentine formation toward Nitze with their deck weapons uncovered. Flares from the destroyer attempt to warn away the patrol boats as they close in on the ship.

Nitze’s crew attempted to hail the boats a dozen times, fired ten warning flares at the patrol boats and blasted the ship’s whistle to sound a maritime danger signal to no apparent effect, a defense official confirmed to USNI News late Wednesday.

Two of the patrol boats came within 300 yards of the destroyer before slowing and breaking off their chase.

“The Nitze and U.S. Naval Forces Central Command (NAVCENT) assessed the interaction as unsafe and unprofessional due to the Iranian vessels not abiding by international law and maritime standards including the 1972 Convention on the International Regulations for Preventing Collisions at Sea (COLREGS) maritime ‘Rules of the Road’,” a defense official told USNI News.

“The Iranian high rate of closure on a Unites States ship operating in accordance with international law while transiting in international waters along with the disregard of multiple warning attempts created a dangerous, harassing situation that could have led to further escalation including additional defensive measures by Nitze.”

Officials said Nitze was operating with the guided-missile destroyer USS Mason (DDG-87) and was exiting the Persian Gulf when Nitze was approached by the Iranian patrol vessels with no warning.

Nitze is part of the Eisenhower Carrier Strike Group, centered on USS Dwight D. Eisenhower (CVN-69). The CSG is in the region conducting strikes against ISIS in Iraq and Syria in support of Operation Inherent Resolve (OIR). In late June, another ship in the strike group — USS San Jacinto (CG-56) — was harassed in the Eastern Mediterranean by a Russian frigate.

Iranian Revolutionary Guard Corps Navy

Unlike the regular Iranian Navy, the IRGCN is a paramilitary organization that reports directly to Iran’s sectarian leadership.

Since 2007, the IRGCN has been responsible for the coastal defense of Iran and has been at the center of several violations of international maritime law involving the U.S. and U.K.

In the same year they started coastal patrols, IRGCN forces captured 15 U.K. Royal Navy personnel embarked in a small boat from HMS Cornwall in international waters.

Last year, the IRGCN captured the U.S. flagged commercial ship M/V Maersk Tigris and held the ship for more than a week in Iran.

In January, the IRGCN captured ten U.S. riverine sailors and held them overnight on Farsi Island after the sailors strayed into Iranian waters.