TEHRAN - Iran's Islamic Revolution Guard Corps (IRGC) on Monday unveiled a map outlining a new "area of control" in the Strait of Hormuz, a narrow waterway through which about a fifth of the world's oil passes.

The map was published by the IRGC's Sepah News outlet, which warned that any vessel failing to comply with Guard naval directives would face "serious risks."

The zone extends from the southern Iranian coast near Kooh Mobarak to the UAE port city of Fujairah on the east, and westward to a line between Iran's Qeshm Island and the UAE emirate of Umm al-Quwain in the Persian Gulf.

IRGC spokesman Hossein Mohebi said the announcement did not represent a change in overall management of the waterway, Sepah News reported. Commercial vessels following transit protocols set by the Guard Navy and coordinating with Iranian authorities along designated routes would be allowed safe passage, he said. Vessels violating those rules could be stopped by force, he warned.

The announcement came a day after President Donald Trump said the United States would help guide ships stranded in the strait out of restricted waters Monday.

Iran's Khatam al-Anbiya Central Headquarters -- the country's top military command -- responded by warning that any foreign forces, particularly US troops, would be targeted if they attempted to enter or approach the strait, according to the official IRNA news agency.

Also on Monday, two missiles struck a US Navy frigate in the strait after it ignored an Iranian warning, the semi-official Fars news agency reported. The vessel had been sailing near the port of Jask in what Iran described as a violation of maritime security rules. The frigate could not continue on its course after the strikes and withdrew from the area, the report said. US officials had no immediate comment.

Iran began tightening its grip on the strait Feb 28, restricting passage for vessels linked to Israel and the United States after both countries launched joint strikes on Iranian territory. The United States later imposed its own blockade measures after post-cease-fire talks between the two sides in Islamabad on April 11-12 failed to produce an agreement.