Iran's Persian Gulf Strait Authority said navigation through the strait was impossible due to what it described as continuing US military aggression, adding that shipping requests would be reconsidered once security conditions improve.
The announcement came as Iran and the United States entered a third day of renewed military exchanges. Iran's Islamic Revolutionary Guard Corps (IRGC) said it launched missiles and drones at US military facilities in the region, including the Ahmad al-Jaber Air Base in Kuwait.
Earlier, the IRGC reported attacking two oil tankers and forcing four others to alter course, accusing them of ignoring Iranian navigation instructions. Regional reports indicated that shipping through the Strait of Hormuz was almost completely disrupted on Friday.
