Maritime access restrictions begin in the Gulf

• Affects Iranian ports and coastal areas
• Vessels ‘may encounter military presence’
• Further pressure on stuck seafarers

Maritime ​access restrictions are ​being enforced affecting Iranian ports and coastal ​areas, including ​locations along the Gulf, ‌the Gulf ⁠of Oman and the Strait of Hormuz, according to the United Kingdom Maritime Trade Operations (UKMTO) agency.
The measures apply to all vessels engaging with Iranian ports, oil terminals and coastal facilities, regardless of flag, and extend across the country’s entire coastline from the Gulf to the Arabian Sea.
The blockade was due to begin at 1800 GST on Monday, according to US Central Command. After the deadline had passed, US President Donald Trump used a Truth Social post to say if any Iranian ships “come anywhere close to our blockade, they will be immediately eliminated”.
Transit through the Strait of Hormuz to and from non-Iranian destinations is not formally restricted, UKMTO said, but vessels “may encounter military presence, directed communications, or right-of-visit procedures during passage”.
Neutral ships currently in Iranian ports have been granted a ”limited grace period to depart”, while further details on enforcement, exemptions and routing are expected to be issued through official notices to mariners.
Guidance on how the restrictions will be applied in practice – including verification and authorised transit procedures – remains under development, with additional advisories expected as the situation evolves.
UKMTO, a Royal Navy-led organisation serving as the primary 24/7 liaison between military forces and commercial shipping, urged vessels operating in the Strait of Hormuz, the Gulf of Oman and nearby waters to maintain heightened situational awareness, ensure maximum bridge readiness and exercise caution in communications as risks remain elevated.

The escalation follows the breakdown of US-Iran talks in Pakistan at the weekend after a two-week ceasefire was announced. Iran’s foreign minister Seyed Abbas Araghchi said on Sunday the sides had been “inches away” from a memorandum of understanding.

An Iranian military spokesperson said security in the Gulf “is either for everyone or for no one”, The New York Times reported. 

“If the security of the ports of the Islamic Republic of Iran in the waters of the Persian Gulf and the Sea of Oman is threatened, no port in the Persian Gulf and the Sea of Oman will be safe,” the spokesperson said.

Jakob Larsen, chief safety and security officer at Bimco, one of the world’s largest shipping associations, said the US move was “not unexpected”, adding that operators he was speaking with had raised concerns about potential breaches of international conventions and the erosion of freedom of navigation.

“The risk of further escalation to involve direct attacks on ships is a concern,” Larsen told AGBI.

As the clock ticked down to the deadline, China urged calm and restraint, with foreign ministry spokesman Guo Jiakun saying the “root cause” of the crisis is the ongoing war. 

Iran’s Kharg Island export terminal, which handles more than 90 per cent of the Islamic Republic’s oil exports, lies about 650km northwest of the strait. It sends more than 80 percent of its seaborne crude to China through the narrow chokepoint.

It is unclear how the US would prohibit vessels linked to the Islamic Republic. 

Further reading:

• Oil up 7% as US set to block ships from Iranian ports
• Why Hormuz is no Suez or Panama
• The Hormuz islands that hold sway over global energy

Many ships transporting Iranian crude have operated under a shadow fleet system in which their Automatic Identification System (AIS) transponders are switched off or spoofed.

Shipping data shows how sharply traffic has fallen since Trump announced the US blockade on Sunday evening. Only three tankers transited the strait between April 12 and 13, down from nine on April 11, according to maritime intelligence firm Pole Star Global.

Normally about 150 vessels transit the Strait of Hormuz each day. In March, a little more than 150 ships passed through the waterway across the entire month, according to S&P Global Market Intelligence.

Vessels have been rerouted north of Larak island through what has been described as an Iranian-approved “Tehran toll booth”. Dozens of ships have used the northern corridor through the strait since March 13, with some operators paying up to $2 million for safe passage, according to Lloyd’s List.

Some 20,000 seafarers remain stranded aboard vessels in and around the Gulf.

The Seafarers’ Charity said the US blockade risked worsening conditions for crews.

“While many details are still to emerge, these latest measures could all too easily pile yet more pressure on civilian seafarers stuck in the Gulf,” a spokesperson told AGBI.

“All parties should prioritise seafarer safety and welfare. Increasing the level of threat and uncertainty for thousands of men and women who have been stuck on their ships in the midst of a conflict zone for weeks is deeply concerning.”