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Three Iranian oil tankers carrying roughly five million barrels of crude have successfully exited the Gulf, marking the first such movement since Washington imposed a blockade on Iran’s oil exports earlier this week. The development raises fresh questions about how tightly the restrictions are being enforced and whether Tehran is continuing to move oil through established workaround channels.

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The vessels — Deep Sea, Sonia I, and Diona — each loaded crude at Iran’s Kharg Island in early April. According to tracking firm Kpler, they passed through the Strait of Hormuz on Wednesday, despite the U.S. naval presence aimed at halting such shipments. It remains unclear whether the ships were allowed to proceed or managed to evade monitoring.

The passage is significant. Since the blockade began on Monday, no Iranian tanker carrying crude had been recorded leaving the Gulf. The last confirmed departure prior to this week was on April 10, before restrictions were tightened.

Tracking the ships has been difficult. Their AIS transponders — standard systems used to broadcast a vessel’s location — have been switched off, a tactic commonly used to obscure movements. Public tracking platforms last recorded the vessels about a month ago near the Strait of Malacca, far from Iranian waters. Kpler instead relied on satellite imagery to confirm that all three tankers transited the strait midweek.

While their immediate destinations are not disclosed, their past behavior offers a strong indication of where they are headed. For several years, these vessels have routinely sailed toward waters near Singapore, where offshore ship-to-ship transfers take place. This process allows Iranian crude to be transferred to other tankers, effectively masking its origin before it is shipped onward.

From there, the oil typically moves to buyers in China. Recent voyage data supports this pattern. Cargo previously carried by the Deep Sea was transferred and ultimately delivered to Yantai in northern China on March 30. The Diona’s earlier shipment reached Dongjiakou on April 10 through a similar transfer chain. The Sonia I’s last cargo was also offloaded via an intermediary vessel, though its final destination could not be confirmed.

The scale of these operations is substantial. Since March 1, at least 37 tankers linked to Iran have conducted ship-to-ship transfers in the Singapore area, moving an estimated 62.3 million barrels of crude, according to Kpler. The activity underscores a well-developed logistics network designed to keep Iranian oil flowing despite sanctions.

Additional vessel movements this week further illustrate the fluid situation. Two sanctioned Iranian container ships exited the Gulf via the Strait of Hormuz but later reversed course near the Pakistan border, returning toward Iranian waters near Chabahar. Meanwhile, two other sanctioned cargo vessels transited the strait inbound and were last tracked near Bandar Abbas.

Together, the movements suggest that while the U.S. blockade has disrupted normal shipping patterns, it has not fully halted Iran’s ability to export oil. Instead, Tehran appears to be relying on a combination of evasive navigation, opaque tracking practices, and offshore transfer hubs to sustain its crude flows into global markets.