Piracy reporting bodies have issued warnings to vessels off Iran and the Philippines after new intelligence emerged.
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.
Meanwhile, the IMB has relayed Malaysian intelligence that an Abu Sayyaf kidnapping gang left Jolo Island in the Philippines on Monday, destined for Sabah, Malaysia.
Security consultancy Ambrey said the target area is understood to be around Felda Sahabat and Tambisan.
The group is said to be using a speedboat painted red on the top and yellow on the bottom with two 40HP outboard engines.
