The U.S. accused Iran of seizing another oil tanker Wednesday in the waters of the Middle East, a move Navy officials said violates international law and destabilizes security in the region.

A dozen boats swarmed the oil tanker Niovi as it transited the Strait of Hormuz at 6:20 a.m. local time, U.S. 5th Fleet spokesman Cmdr. Tim Hawkins said in a statement Wednesday.

The seizure of the Panama-flagged oil tanker follows a similar incident last week when Iran’s navy boarded the Marshall Islands-flagged supertanker Advantage Sweet in the Gulf of Oman.

That was likely in retaliation for American actions to redirect a tanker attempting to ship Iranian crude oil to China, U.S. officials said last week.

The fast-attack watercraft that swarmed the Niovi belong to Iran’s Islamic Revolutionary Guard Corps navy, the 5th Fleet statement said.

“Iran’s continued harassment of vessels and interference with navigational rights in regional waters are unwarranted, irresponsible and a present threat to maritime security and the global economy,” the Navy statement said.

The oil tanker had departed from Dubai and was transiting from the Persian Gulf toward the port of Fujairah in the United Arab Emirates, the statement said.

Niovi is the only ship owned by Grand Financing Co., which is registered in Liberia, the International Maritime Organization shipping database said. The Greece-based Smart Tankers Inc., which operates the ship, did not immediately respond to a request for comment Wednesday.

The Niovi was forced to head toward Bandar Abbas, on the southern coast of Iran, the 5th Fleet said Wednesday.

The port at Bandar Abbas is where Advantage Tankers, which lists the Advantage Sweet as one of its 18 oil tankers, said its ship was being held.

Iran did not issue any official statements regarding the latest seizure as of early Wednesday afternoon. Iran’s semi-official Tasnim news agency reported Wednesday the oil tanker had broken maritime rules, without specifying an infraction. 

Iran and the U.S. have accused each other of being a destabilizing force in the Middle East, which analysts say is locked in a shadow war between Tehran and Washington.

The Navy statement Wednesday said Iran has harassed, attacked or interfered with the navigational rights of 15 internationally flagged merchant vessels over the past two years.

Iran said it intercepted Advantage Sweet because it fled after colliding with a fishing vessel, injuring two crew members, the Iranian state news agency IRNA reported.

But the ship’s operator had no knowledge of any collision, Mark Clark, director of a crisis response company representing Advantage Tankers, said Friday.

An insurance company representative was able to board the Advantage Sweet at Bandar Abbas on April 30 to make sure that the crew was safe, Clark said Wednesday.