Memos 
Live events & webinars 
Trend Reports
Iran seized an oil tanker in the Strait of Hormuz on Wednesday, the US Navy said, in the second such capture in less than a week.
The US Navy's Fifth Fleet, based in Bahrain, said in a statement that naval forces of Iran’s Islamic Revolutionary Guard Corps (IRGC) swarmed the Panama-flagged Niovi vessel while it was en route to the port of Fujairah in the United Arab Emirates after having departed Abu Dhabi. The vessel was forced to change course and head into Iranian territorial waters towards Bandar Abbas in what the US Navy described as an “unlawful seizure.”
“Iran’s actions are contrary to international law and disruptive to regional security and stability. Over the past two years, Iran has harassed, attacked or interfered with the navigational rights of 15 internationally flagged merchant vessels,” the Fifth Fleet added in its statement.
US Navy forces based in the Gulf region did not receive a distress call from the Niovi, but a US fixed-wing unmanned aircraft patrolling over the strait witnessed the IRGC seizure, spokesperson Cdr. Tim Hawkins told Al-Monitor.
Iranian media cited Tehran's chief prosecutor's office as saying the vessel had been seized over an unspecified legal complaint.
The US State Department on Wednesday condemned Iran's move, urging it to immediately release the Panama-flagged vessel.
“Iran’s harassment of vessels and interference with navigational rights in regional and international waters are contrary to international law and disruptive to regional stability and security,” spokesman Vedant Patel told reporters.
Greece, which hosts many international ships, reportedly warned vessels to avoid the area near Iranian waters in the days before the attack.
“We strongly recommend the navigation in the above area as well as in the Straits of Hormuz and the Gulf of Oman to be carried out, if possible, outside the waters under Iran's jurisdiction, and under increased caution when sailing near the above areas,” according to documents dated April 20 from the Greek Shipping Ministry, as reported by Reuters on Wednesday.
Second attack in six days
The seizure comes less than a week after the Iranian Navy seized another commercial tanker in the Gulf of Oman. Iranian naval forces boarded the US-bound, Marshall Islands-flagged tanker Advantage Sweet – which was carrying Kuwaiti crude oil and contracted by Chevron – and directed it to Iranian waters on Apr. 27.
US officials said that seizure came in retaliation for the US Justice Department ordering the crew of another Marshall Islands-flagged tanker, the Suez Rajan – which was carrying Iranian crude oil bound for China – to redirect to the United States for seizure.
In 2020, the US seized the Iranian-owned fuel onboard four tankers en route to Venezuela and sold it in part to compensate American citizens whose family members had been victims of terrorist attacks. A bipartisan group of US lawmakers last week urged the Biden administration to continue seizing shipments of sanctioned Iranian fuel.
It remains unclear if the IRGC's seizure of the Niovi on Wednesday was related to those incidents. A Western source familiar with the incident but speaking not for attribution told Al-Monitor the Niovi was not carrying petroleum cargo at the time it was seized.
Tensions between Washington and Tehran have only gotten worse after the former Trump administration pulled out of the Iran nuclear deal in 2018, in a move Gulf countries say helped Tehran expand its influence in the region.
Since then, attacks on oil vessels in the Gulf waters have increased. The US blamed Iran for explosions that targeted two oil tankers near the Strait of Hormuz back in 2019. In 2021, two crew members were killed in a suspected drone attack on an Israeli-owned ship in the Gulf of Oman, which was also pinned on Iran.
Earlier this month, Iran claimed to have forced a US cruise-missile submarine to surface in the Strait of Hormuz after it entered Iranian territorial waters. The US Navy categorically denied the claims.
“Iran's claim is absolutely false. A US submarine has NOT transited the Strait of Hormuz recently. The claim represents more Iranian disinformation that destabilizes the region,” the Fifth Fleet said on Twitter.
That Iranian claim came days after the US Navy deployed the USS Florida capable of carrying 154 Tomahawk cruise missiles into Middle East waters via the Suez Canal in support of its Fifth Fleet.
The spate of attacks in the Gulf also coincide with a landmark China-brokered normalization deal reached between Saudi Arabia and Iran in March, which some analysts say reflects the US’ waning influence in the region.
Editor's note: this article was updated on May 4, 2023, to include comment from the US State Department. With reporting from Jared Szuba in Washington, DC.
