A US Navy attack submarine has sunk an Iranian warship in the northern Arabian Sea with a single torpedo strike, US defence sources say, marking the most dramatic naval clash of the spiralling US–Iran confrontation.

The Virginia‑class submarine reportedly tracked the Iranian frigate for hours as it maneuvered near key sea lanes used by oil tankers. When the ship allegedly moved into what US commanders describe as a “hostile posture,” the sub fired a heavyweight torpedo that slammed into the vessel’s port side, ripping open its hull and knocking out power within seconds.

Flaming debris and an expanding oil slick were still visible at first light as rescue helicopters from nearby coalition vessels winched desperate sailors from the water. Initial estimates suggest more than 150 crew were on board; dozens are feared dead or missing. Tehran has branded the strike a “cowardly ambush in international waters” and vowed a “crushing response.”

Pentagon officials counter that the warship had been providing targeting data for Iranian missiles and drones launched at US bases and commercial shipping, calling the engagement “self‑defence in accordance with international law.”

For global markets and regional capitals, the message is chilling: the shadow war in the Gulf has burst into the open, and heavy steel is now going to the bottom. The question hanging over every capital tonight is simple and brutal — does this sinking restore deterrence, or ignite a wider naval war that no one can control?