Reports describe a U.S. maritime enforcement action in the Gulf of Oman in which U.S. Marines boarded and U.S. authorities seized an Iran-linked, Iranian-flagged tanker carrying more than 1 million barrels of crude oil. The supplied material frames the incident as a sanctions-related action tied to Iranian oil trade, though it does not identify the vessel, timing, legal authority, destination, or cargo value. Because the Gulf of Oman is a key energy shipping corridor linked to the Strait of Hormuz, the development heightened U.S.-Iran tensions and raised concerns about oil shipping security, energy market sensitivity, and broader risk sentiment.