On May 20, 2026, the US military conducted an operation to seize the oil tanker M/T Celestial Sea in the Gulf of Oman. According to Reuters, citing a statement from the US Central Command (CENTCOM), US Marines boarded the vessel, which the US suspected was violating the US naval blockade against Iran.

CENTCOM clarified that after the inspection, the tanker was released, and its crew was ordered to divert course. The vessel was en route to an Iranian port.

The incident was part of an ongoing US campaign to interdict Iran's so-called "shadow fleet"—a network of vessels that use flag spoofing and navigational systems to evade sanctions and transport Iranian oil. Monitoring data shows the M/T Skywave, also under sanctions, was moving west of Malaysia on May 19 before being intercepted by US forces. The seizure was at least the third such incident in recent weeks as part of Washington's efforts to disrupt Iran's funding, which the US claims is used, among other things, to support proxy forces in the region.

Official Tehran has not yet commented on the tanker seizure. The situation is unfolding amid ongoing military and political tensions in the region following the start of the US and Israeli military operation against Iran in late February 2026. Despite a formal ceasefire, the two sides periodically exchange strikes, and Iranian forces in the Persian Gulf and the Strait of Hormuz continue to detain or attack vessels they believe violate the rules.