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MSCI Advisory

2023-003-Persian Gulf, Strait of Hormuz, Gulf of Oman, Arabian Sea, Gulf of Aden, Bab al Mandeb Strait, Red Sea, and Somali Basin-Threats to Commercial Vessels


This advisory replaces U.S. Maritime Advisory 2022-008

1. References: U.S. Maritime Advisory 2022-010, U.S. Maritime Alerts 2022-001A, 2022-002A, 2022-003A, and 2023-001A.

2. Issues and Specific Guidance: Regional conflict, military activity, and political tensions pose threats to commercial vessels operating in the above listed geographic areas. The U.S. government is continually assessing the maritime security situation in the region to safeguard freedom of navigation; ensure the free flow of commerce; and protect U.S. vessels, personnel, and interests. Additionally, the international community, including the U.S., continues maritime security operations within this region. While some past incidents may have targeted specific commercial vessels due to their association with certain countries, individuals, or companies, not all did, and the potential remains for miscalculation or misidentification that could lead to aggressive actions against non-associated commercial vessels. Heightened regional tensions in the listed areas, caused by an array of geopolitical issues, could result in an increased threat level to commercial vessels, as noted in Maritime Alert 2023-001A. The following are currently deemed to be the most pressing threats to U.S. flagged commercial vessels in these areas, in no particular order:

a) UAVs: Explosive unmanned aerial vehicle (UAV) attacks on commercial vessels in the listed areas, other than the Somali Basin, remain a threat. The most recent UAV attack in this region was on the Liberian flagged M/V CAMPO SQUARE on February 11th of this year.

- If U.S. flagged commercial vessels observe or hear a suspected UAV, they should immediately inform the U.S. Fifth Fleet Battle Watch. Crewmembers not needed for the safe navigation and operation of the vessel should be relocated to a safe space on the vessel until the threat has passed.

b) Iranian Boarding/Detention/Seizure: Multiple commercial vessels transiting through the Persian Gulf, Strait of Hormuz, and Gulf of Oman have been boarded and detained or seized by Iranian forces over the past several years. Recent incidents include the Iranian seizure of two Greek-flagged tankers in the Persian Gulf in May 2022. Iranian forces have utilized small boats and/or helicopters during boarding operations and have attempted to force commercial vessels into Iranian territorial waters.

- If hailed by Iranian forces, U.S. flagged commercial vessels should provide vessel name, flag state, and affirm that they are proceeding in accordance with international law as reflected in the Law of the Sea Convention. The master should immediately inform the U.S. Fifth Fleet Battle Watch of such queries.

- If Iranian forces seek to board a U.S. flagged commercial vessel navigating these waters, the ship’s Master should, if the safety of the ship and crew would not be compromised, decline permission to board, noting that the vessel is proceeding in accordance with international law, as reflected in the Law of the Sea Convention, and immediately inform the U.S. Fifth Fleet Battle Watch.

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

c) Limpet Mines: Limpet mines have been used to damage commercial vessels on multiple occasions in recent years and are primarily a threat to commercial vessels in the Persian Gulf, Strait of Hormuz, and the Gulf of Oman. Limpet mines, or similar improvised explosive devices, can be attached to vessel hulls, above or below the waterline, via swimmers or small boats, while a vessel is berthed, at anchor, or underway.

- When operating in these waters, U.S. flagged commercial vessels should maintain a close lookout and remain vigilant for suspicious activity to include the approach of swimmers or small boats. Close attention should be given to the vessel’s waterline, especially at slow speeds, at anchor, and when moored.

- If crewmembers believe a mine has been, or was attempted to have been, attached to their vessel, they should immediately inform the U.S. Fifth Fleet Battle Watch. Crewmembers not needed for the safe navigation and operation of the vessel should be relocated to a safe space on the vessel until the threat has passed.

d) Explosive Boats: Explosive boat attacks are a known threat to commercial vessels operating in the Red Sea, Bab al Mandeb Strait, and the Gulf of Aden. Vessels in these areas have reported explosions believed to have been caused by explosive boats, both in port and underway.

- When operating in these waters, U.S. flagged commercial vessels should maintain a vigilant lookout at all times for small boats operating in a suspicious manner and additional precautions should be taken to ensure small boats are kept at a safe distance whenever possible.

- If crewmembers believe an attempted explosive boat attack is underway, or was attempted, they should immediately inform the U.S. Fifth Fleet Battle Watch. Crewmembers not needed for the safe navigation and operation of the vessel should be restricted to a safe location on the vessel until the threat has passed.

e) Yemen Conflict: The conflict in Yemen continues to pose a risk to U.S. flagged commercial vessels in the Red Sea, Bab al Mandeb Strait, and Gulf of Aden. The UN-brokered truce in Yemen expired on October 2nd, 2022. As outlined in Maritime Alert 2022-003A, two drone strikes targeted the al-Dhabba oil export terminal in al-Shihr, Yemen, while tankers were attempting to load cargoes of crude oil. In addition to threats otherwise referenced in this advisory, additional threats include, but are not limited to, missiles, rockets, projectiles, mines, and small arms. These threats pose a direct or collateral risk to U.S. flagged commercial vessels transiting in international shipping lanes, or otherwise operating in these areas.

- U.S. flagged commercial vessels operating in these areas are advised to avoid entering or loitering near Yemen's ports, and exercise increased caution if operating in Yemen’s territorial waters or Saudi territorial waters on the Red Sea. Crewmembers should be especially vigilant if at anchor, operating in restricted maneuvering conditions, or proceeding at slow speeds.

f) Navigation or Communication Disruptions: Vessels operating in these areas may encounter GPS interference (see Advisory 2022-010), AIS spoofing, bridge-to-bridge communications spoofing, and/or other communications jamming. Vessels have also reported bridge-to-bridge communications from unknown entities falsely claiming to be U.S. or coalition warships, or the Yemeni Government.

- In addition to risks to navigation, confusion from such disruptions could be leveraged by bad actors to facilitate physical attacks. Additional precautions should be taken if your vessel experiences, or vessels in your vicinity report experiencing, such disruptions.

- If a U.S. flagged commercial vessel suspects it is being hailed from a source falsely claiming to be a U.S. or coalition naval vessel or is being asked for positions or info on coalition military vessels or aircraft operating in the area, the U.S. Fifth Fleet Battle Watch should be immediately informed.

- Maritime GPS disruptions or anomalies should be reported immediately to the USCG Navigation Center (NAVCEN), available 24 hours a day.

g) Piracy and Armed Robbery at Sea: Piracy and armed robbery continue to pose a threat to commercial vessels operating in the Gulf of Aden, Western Arabian Sea, and Somali Basin. Specific case details are available via the Office of Naval Intelligence's weekly "Worldwide Threat to Shipping" product at

- The Best Management Practices to Deter Piracy and Enhance Maritime Security in the Red Sea, Gulf of Aden, Indian Ocean and Arabian Sea (BMP5), and Maritime Global Security website at: should be consulted prior to operating in the above listed geographic waters.

- Transit by yachts and privately owned sailing vessels through the region is hazardous and may result in capture. The U.S. Government advises against all operation of yachts and pleasure craft in these areas. American citizens abroad should inform the nearest U.S. embassy or consulate of their plans to transit the area and/or update their information via the Smart Traveler Enrollment Program (STEP) at: Yachting guidance can be found at:

h) Suez Canal Southern Anchorage: Maritime Alert 2022-001A informed that maritime incidents had been reported in the northern Red Sea, Suez Canal southern anchorage. These incidents occurred in the vicinity of 29-50N 032-34E, approximately 7 nautical miles south of Port Tawfiq, Egypt, on September 8th and 21st, 2022. The nature of these reported incidents was unlawful boarding and theft aboard commercial vessels at anchor. Exercise caution when anchoring in this area.

3. General Guidance: U.S. flagged commercial vessels operating in these waters are advised to exercise caution, review security measures, ensure AIS is transmitting at all times (except in extraordinary circumstances), in accordance with provisions of the International Convention for Safety of Life at Sea (SOLAS), and monitor VHF Channel 16. To afford best protection in the region, U.S. flagged commercial vessels are also advised to:

- Coordinate vessel voyage planning for transits in the region with the International Maritime Security Construct (IMSC) and follow their recommendations and guidance whenever possible. IMSC has the latest information on the current maritime security threats and the operational environment in this region. IMSC organizational information is available at The Fifth Fleet Naval Coordination and Guidance for Shipping (NCAGS) detachment that previously served as the primary POC in this region for U.S. maritime industry stakeholders is no longer deployed to Fifth Fleet.

- Simultaneously register with both the United Kingdom Maritime Trade Office (UKMTO) and the IMSC watch 24 hours prior to entering the Indian Ocean Voluntary Reporting Area by sending UKMTO and IMSC, via a single e-mail, the Initial Report from Annex D of (BMP5). Include the estimated times of arrival at the Suez Canal, Bab el Mandeb Strait (BAM), and Strait of Hormuz (SoH) in line 10 of the report and add a line 14 for comments as needed (e.g., speed restrictions or other constraints, anticipated time of entering/exiting the SoH Traffic Separation Scheme; an outline of the navigation plan for operating in the SoH and Persian Gulf, etc.). Utilize other reports included in Annex D of BMP5 as necessary.

- Answer all VHF calls from coalition navies. Vessels should be aware that U.S. and other coalition naval forces may conduct maritime awareness calls, queries, and approaches to ensure the safety of vessels transiting these listed waters.

- In the event of any incident or suspicious activity, immediately contact the U.S. Fifth Fleet Battle Watch, IMSC, and activate the Ship Security Alert System.

- Vessels operating in this area are advised to establish contact with both UKMTO and the IMSC watch, and to include both on all updates or incident report emails, as detailed above. By including both as addressees on each email, awareness will be enhanced without creating an additional reporting burden.

- Due to the risk of piracy, kidnapping, hijacking, and robbery while operating within U.S. Coast Guard designated High Risk Waters (HRW), U.S. flagged commercial vessels are required to comply with the Guidelines for U.S. Vessels Operating in High Risk Waters contained in U.S. Coast Guard Maritime Security Directive 104-6 (Rev 8) and comply with their Coast Guard approved Vessel Security Plan annex on counter piracy. The U.S. Coast Guard Office of Commercial Vessel Compliance (CG-CVC) announced in the Federal Register in August 2021 the availability of Revision 8 to Maritime Security (MARSEC) Directive 104–6. U.S. vessel owners and operators who need to take action under previous versions of MARSEC Directive 104–6 should immediately contact their local Coast Guard Captain of the Port or District Commander for a copy of Revision 8.

- Conduct a pre-voyage risk assessment and incorporate appropriate protective measures into their vessel security plans.

- The Maritime Global Security website at offers industry issued best practices and guidance to mariners by geographic region and provides contact and subscription information for regional maritime security reporting centers, particularly in high risk-areas. The Global Counter Piracy Guidance for Companies, Masters and Seafarers, should be reviewed.

- Per 33 CFR 101.305, report all suspicious activities, breaches of security, and transportation security incident events involving U.S. vessels or persons to the U.S. Coast Guard National Response Center. Additional U.S. Coast Guard port specific requirements may be found in Port Security Advisory 2-20 at

- U.S. Department of State Travel Advisories discuss safety and security information that should be reviewed by U.S. mariners prior to disembarkation or embarkation in foreign ports. These travel advisories are available at:

4. Contact Information:

a) Fifth Fleet Battle Watch: + 973-1785-3879, and email details to:

b) IMSC: or +973-1785-8412.

c) UKMTO: or +44 (0) 2392 222060. UKMTO advisories and warnings are available at

d) U.S. Coast Guard National Response Center: +1-800-424-8802.

e) USCG NAVCEN: or +1-703-313-5900.

f) For maritime industry questions about this advisory, contact Supplemental information may also be found on the MARAD Office of Maritime Security website at:

5. Supplemental information about U.S. Maritime Alerts and Advisories, including subscription details, may be found at: Maritime industry stakeholders who wish to receive U.S. Maritime Alerts and Advisories via email should send requests to Feedback provided by U.S. maritime industry stakeholders regarding the U.S. Maritime Advisory System has greatly supported the USG in pursuing continued enhancements to this system. Feedback to is always welcome.

6. Cancellation of Prior Advisories: This message supersedes and cancels U.S. Maritime Advisory 2022-008.

7. This advisory will automatically expire on August 22, 2023.