A US-flagged boxship has reported being surrounded by heavily armed Iranian patrol boats on Thursday in the Strait of Hormuz.
Security consultancy Ambrey said the incident took place 16 nautical miles south-east of Abu Musa at 0300 UTC.
The vessel is not being named, but it is a feedership outbound from Jebel Ali in the United Arab Emirates.
It was approached by four boats, the occupants of which identified themselves as Iranian forces.
The patrol vessels were described as grey and 20 to 30 feet length , with a canopy across the bow.
The master was asked via Channel 16 for details of the crew, including their nationality, and the type of cargo carried on board.
Ambrey said: "No attempt was made to divert or board the boxship. Crew attempted to hail coalition warships but did not receive an answer. The patrol vessels departed shortly thereafter."
Earlier this week, UK Maritime Trade Operations (UKMTO) said a cargoship was approached by two suspicious skiffs in the Tunb-Farur eastbound traffic separation scheme in the Strait of Hormuz on 27 March, 23 nautical miles from the Iranian coast.
The boats had five or people on board. A raised ladder was sighted.
The cargo vessel took evasive action and the perpetrators are understood to have discontinued their approach.
The incident occurred 26 nautical miles north of where Stena Bulk's 50,000-dwt tanker Stena Impero (built 2018) was seized by Iranian forces last July, at a time of high tension with the UK over the detention of the VLCC Grace 1 off Gibraltar.
Piracy thought to be unlikely
Security consultancy Dryad Global said: "Currently the advisory is not classified as a maritime security event and has not been verified.
"Reporting within this area is highly irregular. It remains assessed as highly unlikely that Iran would seek to conduct disruptive activity within this area at this time."
Fishing traffic remains common throughout the area, as does illicit trading, Dryad added.
"Maritime crime in the form of intended illegal boardings of vessels underway, originating from Iran or any of state within the Persian Gulf would be a highly irregular occurrence," it said.