MARAD Warns of Iranian GPS Jamming in Strait of Hormuz

alt — A U.S. official told CNN that Iran has deployed GPS jammers on the island of Abu Musa, lower left (file image)

In a new advisory issued this week, the U.S. Maritime Administration warned that vessels may encounter GPS jamming, misleading communications and other harassment from Iranian forces in the Persian Gulf region.

Tensions in the region pose serious threats to commercial vessels, MARAD warned. Vessels operating in the Persian Gulf, Strait of Hormuz, and Gulf of Oman may encounter "GPS interference, bridge-to-bridge communications spoofing, and/or other communications jamming with little to no warning."

MARAD said that in at least two of the many incidents that have occurred since May, vessels reported GPS interference, and other ships have reported fake bridge-to-bridge comms from "unknown entities falsely claiming to be U.S. or coalition warships."

An American official told CNN Wednesday that Iran is believed to have GPS jammers located on the island of Abu Musa, which is located at the eastern entrance to the strait. The Iranian objective, the official said, is to trick vessels into straying into Iranian-controlled waters in order to justify a seizure. Iranian military vessels have also been transmitting fake AIS signals to disguise themselves as merchant ships, the official said.

Incidents attributed to Iran over the past several months include the six limpet mine attacks on tankers in the Gulf of Oman in May and June; the attempt to harass or capture the Red Ensign-flagged tanker British Heritage; the successful boarding and seizure of the UK-flagged tanker Stena Impero; the seizure of the small tanker Riah on fuel-smuggling charges; and the boarding and release of the UK-controlled tanker Mesdar.

MARAD issued guidance for American shipping the region to minimize chances of Iranian interference and improve the ability of U.S. Navy and coalition forces to respond in the event of an incident. Masters are advised to:

- Ensure AIS is transmitting at all times

- Monitor VHF Channel 16

- Register with both the United Kingdom Maritime Trade Office (UKMTO) and U.S. Fifth Fleet Naval Cooperation and Guidance for Shipping (NCAGS) Watch when entering the Indian Ocean Voluntary Reporting Area (VRA)

- Provide detailed transit plans for the Strait of Hormuz (SoH) and Persian Gulf (PG) to UKMTO and U.S. Fifth Fleet NCAGS

- In the event of any incident or suspicious activity, call UKMTO or Fifth Fleet and activate the SSAS

- Answer all VHF calls from coalition navies

- Report any calls from a source falsely claiming to be a U.S. or coalition naval vessel to Fifth Fleet.

- If hailed by Iranian forces, U.S. flag commercial vessels should affirm that they are proceeding in accordance with international law and notify Fifth Fleet

- If Iranian forces seek to board a U.S. flag commercial vessel, the ship’s Master should, if the safety of the ship and crew would not be compromised, decline permission to board and immediately notify Fifth Fleet

- If Iranian forces board a U.S. flagged commercial vessel, the crew should not forcibly resist the boarding party. Refraining from forcible resistance does not imply consent or agreement to that boarding.