The UK Maritime Trade Operations (UKMTO) agency said it had received multiple reports from vessels operating in the Arabian Gulf that radio broadcasts had claimed the Strait of Hormuz had been closed, but it said it could not independently confirm those reports.
In an advisory issued on Friday, UKMTO said Company Security Officers for ships in the region had reported that VHF Channel 16 broadcasts stated the Strait of Hormuz (SoH) “has been closed”. “These reports cannot be independently verified at this time,” UKMTO said in the update, dated 28 Feb at 0700 UTC.
There was no immediate confirmation from Iran, Reuters reported.
The advisory was issued amid what UKMTO described as “significant military activity” in the Arabian Gulf, Gulf of Oman, North Arabian Sea and the Strait of Hormuz, warning mariners of an increased risk environment and potential disruption to shipboard systems.
UKMTO said mariners should note “the potential for elevated electronic interference, including disruption to AIS and other navigational or communications systems”. AIS refers to the Automatic Identification System used by ships to broadcast their position and identity, a key safety tool in congested waterways.
While acknowledging the reports of closure messages, UKMTO stressed that radio broadcasts alone would not amount to a lawful restriction on passage. “VHF broadcasts or statements indicating closure of the Strait of Hormuz are not legally binding and do not constitute a lawful restriction on navigation under international law, including the United Nations Convention on the Law of the Sea (UNCLOS), unless implemented and enforced in accordance with applicable legal frameworks,” the advisory said.
It added that, while military forces may establish advisory or warning zones to reduce the risk of inadvertent engagement, “this is not intended to impede neutral or merchant shipping, and vessels remain free to navigate international waters”.
UKMTO urged vessels transiting the area to take additional precautions, including conducting enhanced risk assessments, maintaining a listening watch on VHF Channel 16 and being prepared to respond to hails. It also warned crews to be alert to the risk of misidentification and the effects of electronic interference, and said ships could consider increasing distance from military units where practicable to reduce risk.
The agency advised ships to report suspicious activity, “kinetic activity”, electronic interference or abnormal radio communications to UKMTO or the Maritime Security Centre – Indian Ocean, noting that the situation was “extremely dynamic” and that further updates would be issued as information became available.
The Strait of Hormuz, a narrow sea passage between Iran and Oman, is widely regarded as the world’s most important oil transit chokepoint. It links major Gulf oil producers — including Saudi Arabia, Iran, Iraq and the United Arab Emirates — with the Gulf of Oman and the Arabian Sea, providing the main maritime出口 route for crude oil and petroleum products shipped from the Gulf to international markets. Around a fifth of global oil shipments pass through the strait, according to widely cited estimates.
Even unverified reports of disruption can have immediate effects for commercial shipping, including delays, rerouting decisions and higher operating costs. Industry sources and reporting in recent weeks have pointed to rising concerns among shipowners and insurers about the security situation in the Gulf, with war-risk cover becoming more expensive and, in some cases, being withdrawn or re-priced for voyages through the area.
The latest UK advisory follows a series of maritime security alerts in February. Earlier this month, UKMTO reported an incident involving armed small craft that attempted to intercept a commercial vessel within the Strait of Hormuz traffic separation scheme north of Oman, according to reports at the time. In mid-February, Iran announced temporary restrictions in parts of the waterway during military drills, prompting warnings to shipping and renewed focus on the vulnerability of the route.
Friday’s advisory comes as the wider region has been on heightened alert amid escalating military tensions involving Iran, the United States and Israel, with international media reporting strikes and retaliatory actions across the region. UKMTO did not attribute the VHF messages to any particular actor, and its update focused on navigational safety, communications reliability and the need for vessels to report unusual activity.
For now, UKMTO said it was monitoring developments but underscored that the closure claims circulating on marine radio could not be verified independently, leaving the operational status of the strait, and the extent of any enforcement action, unclear.