An Islamic Revolutionary Guard Corps speed boat in the Persian Gulf near a general cargo vessel during the IRGC marine parade on April 29, 2024.

Morteza Nikoubazl | Nurphoto | Getty Images

The threat level to ships crossing the Strait of Hormuz has increased to "severe" after several Iranian attacks on tankers, a naval coalition led by the U.S. warned merchant vessels Tuesday.

The Joint Maritime Information Center cautioned mariners that "deliberate hostile action" by Iran is "likely under current conditions." The center, headquartered in Bahrain, coordinates between allied navies and merchant ships in the Middle East.

Iran agreed to safe passage for commercial ships through Hormuz under the terms of an interim deal it signed with the U.S. on June 17. But Tehran has subsequently launched a series of attacks on ships using a U.S. Navy protected route through the strait.

"There is obviously a battle for control, because obviously the only leverage Iran has is control of Hormuz," said Michelle Wiese Bockmann, a London-based senior maritime intelligence analyst at Windward.

Qatar held Iran responsible for an attack Tuesday on one of its liquified natural gas (LNG) tankers, Al-Rekayyat, near Hormuz. Doha called on Iran to stop endangering global energy supplies.

The United Kingdom Maritime Trade Operations Centre has received three separate reports of tankers coming under attack in or near Hormuz this week. The UKTMO is a maritime security advisory service.

Hormuz has fractured into separate corridors controlled by the U.S. and Iran. The Gulf states are using a southern route that hugs Oman's coast and is protected by the U.S. Navy, Bockmann said.

But Iran's military has warned it will target ships that do not use a northern route approved by Tehran. Vessels are avoiding the traditional route through the middle of Hormuz that Iran mined.

"This is part of this sporadic targeted campaign by Iran to destabilize that southern corridor and send a message to Gulf State producers that are not sending their oil via that northern corridor," Bockmann said.

U.S. Energy Secretary Chris Wright claimed last month that the U.S. Navy corridor had ended Iran's ability to close the strait. Iran subsequently attacked a cargo ship using the route. The U.S. retaliated by launching a renewed round of airstrikes against Iran.

Ship traffic through Hormuz has increased since the U.S. and Iran signed an interim peace deal but remains far below prewar levels.

The trade intelligence firm Kpler verified more than 100 ship passed through Hormuz over the weekend. Oil exports through the strait averaged around 4.3 million barrels per day in June, according to Windward data.

By comparison, more than 100 ships transited Hormuz daily before the war and crude exports totaled more than 15 million bpd.

"The strait remains far from fully functioning," Bockmann said.