Three Iranian crude oil tankers steamed past the US-declared blockade line in the Gulf of Oman, ship-tracking records show, in what maritime analysts say is a clear sign Tehran is restarting shipments. The vessels — Diona, Hero II and Sonia I — are all flagged to Iran and owned by the National Iranian Tanker Company (NITC), a firm and a fleet targeted by US Treasury sanctions.
Two of the ships were transmitting their positions as they crossed the line; a third switched on its transponder shortly after clearing it. Windward Maritime Intelligence and publicly available platforms such as MarineTraffic recorded the movements. Windward says this is the first time any of the three have broadcast locations since March, and TankerTrackers.com says that if the cargoes reach their destinations they would mark Iran’s first crude exports in about two months.
Together the three tankers are carrying roughly 3.8 million barrels of crude, according to TankerTrackers.com. None of the ships are currently reporting planned destinations.
The blockade line, which the US has drawn between the eastern tip of Oman and the Iranian coast across the Gulf of Oman, remains a focus of US maritime enforcement. President Donald Trump had tweeted that the blockade would be “immediately” removed, but US naval commanders later said the restriction would stay in effect until a deal with Iran is formally signed — a ceremony expected in Switzerland on Friday. “This is a sign that Iran is confident the blockade is over, even if the US has insisted it will be in place until Friday,” Michelle Wiese Bockman, a senior analyst at Windward, told BBC Verify.
US officials have previously warned that enforcement of sanctions and the blockade can occur beyond the Gulf region. BBC Verify has documented past US operations intercepting Iran-linked tankers in the Indian Ocean, thousands of miles from the Gulf. In one cited case the sanctioned tanker Tifani was intercepted more than 10 days after leaving the Gulf.
Ship-tracking data shows Hero II and Sonia I departed Iran’s southeastern port of Chabahar on Tuesday and transited past the blockade line into the Arabian Sea in the early hours of Wednesday. Diona began broadcasting only after it had cleared the line. Another NITC vessel, the crude tanker Stream, stopped transmitting before the blockade line and appears to be heading back toward Iran; tracking data indicates Stream has been circling off Karachi, Pakistan since 8 May.
The recent movements are part of wider renewed activity by Iranian-linked commercial tonnage, observers say. United Against Nuclear Iran (UANI), a monitoring and advocacy group, noted a marked increase in activity by Iranian tankers and cargo ships around the globe since the US announced a deal with Tehran. Two other NITC-owned crude tankers, Dan and Sinopa, resumed broadcasting in the Strait of Malacca between Malaysia and Indonesia on Tuesday after months of silence; both now appear to be steaming toward Iran.
US sanctions and the blockade have taken a heavy toll on Iran’s oil exports. Data from maritime intelligence firm Kpler shows Iran’s crude exports fell to about 260,000 barrels per day in May, the lowest level in six years and under a fifth of the 2025 average of 1.67 million barrels per day.
Analysts say Tehran is moving quickly to put its fleet back into commercial service should restrictions be lifted. “Iran is wasting no time getting its tankers back into circulation,” Bockman said.
Reporting by Thomas Copeland and Shruti Menon, BBC Verify. Additional reporting by Barbara Metzler.
