Iran's Islamic Revolutionary Guard Corps (IRGC) has declared the Strait of Hormuz closed to all maritime traffic "until further notice," state media reported early Sunday.
The announcement follows the military unit firing warning shots at a vessel it accused of taking an "unauthorized route" through the narrow waterway.
The closure represents a severe escalation in shipping risk for the corridor, which handles roughly one-fifth of the world's oil supply.
Markets are likely to react to the heightened threat of physical disruption to tanker flows, with Brent crude and shipping equities facing immediate pressure from the uncertainty.
The move signals a shift from rhetorical threats to operational blockades, raising the stakes for global energy security.
This development follows earlier reports that Europe was considering voluntary tolls for Strait of Hormuz transit, a diplomatic maneuver that appears to have been overtaken by the IRGC's hardline stance.