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A few Iran-linked vessels are making their way through the Strait of Hormuz, as the crucial waterway remains effectively closed to most international shipping amid blockades by both Tehran and the US.

Just a single Iran-linked fuel tanker was observed entering the Persian Gulf on Thursday morning, with no exits for the day recorded so far, according to vessel-tracking data compiled by Bloomberg. That follows just three outbound and two inbound transits of dry cargo ships on Wednesday, most of which have ties to Tehran.

Brent crude futures earlier hit a four-year high amid the supply disruption. The US and Iran show little sign of breaking an impasse and agreeing to more peace talks, with President Donald Trump insisting that his blockade is working. Meanwhile, Iran’s new supreme leader vowed not to give up the country’s nuclear or missile technologies and signaled it would keep control of Hormuz.

Ship Movements

Following Wednesday’s departure of two bulk carriers and one container ship tied to Iran, outbound traffic remained at a standstill through Thursday morning.

Recent Iran-linked departures have largely stalled in the Gulf of Oman, though it’s unclear if the ships are following regional itineraries or are being trapped by the US Navy blockade stationed further east outside the gulf.

Vessels transiting Hormuz with active Automatic Identification System signals during the past day were confined to the narrow northern lane approved by Tehran.

Inbound transits over the last 24 hours saw two bulk carriers arrive Wednesday, followed by an Iran-linked fuel tanker on Thursday morning.

The US blockade may encourage Iran-linked ships entering or leaving the Persian Gulf to switch off their signals to avoid detection, making it harder to get an accurate picture of traffic. That means transit figures may sometimes be revised higher when vessels reappear far away from the riskiest waters.

Even before the US imposed its latest restrictions, it was common for Iran-linked ships to stop sending signals as they headed into Hormuz to exit the Persian Gulf. They generally didn’t enable them again until well into the Strait of Malacca in Southeast Asia, about 13 days’ sailing from Iran’s Kharg Island.

NOTES:

Because vessels can move without transmitting their location until they’re well away from Hormuz, automated positioning signals were compiled over a large area covering the Gulf of Oman, the Arabian Sea and the Red Sea to detect those that may have departed or entered the Persian Gulf.

When potential transits are identified, signal histories are examined to determine whether the movement appears genuine or is the result of spoofing — where electronic interference can falsify the apparent position of a ship.

Some transits may not have been detected if vessels’ transponders haven’t been switched back on. Iran-linked oil tankers often steam from the Persian Gulf without broadcasting signals until they reach the Strait of Malacca about 10 days after passing Fujairah in the UAE. Other ships may be adopting similar tactics and won’t show up on tracking screens for many days.

This tracker will be published during heightened tensions involving Iran, and aims to capture traffic for all classes of commercial shipping.

Top photograph: Oil tankers navigates the sea near Qeshm Island, Iran, in the Strait of Hormuz on April 28, 2026; photo credit: Asghar Besharati/Getty Images

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