A lethal attack on an oil tanker which killed one British and one Romanian national used explosive drones also known as "loitering munitions", the US military confirmed on Saturday.
The tanker Mercer Street is linked to an Israeli billionaire and was attacked in the Arabian Sea on Thursday evening. An Israeli official told The New York Times that the drones had been flown directly into living quarters underneath the ship's bridge, implying a deliberate attempt to cause loss of life.
"Initial indications clearly point to a UAV-style attack," read a statement from US Centcom, the US military general headquarters in the Middle East, in reference to unmanned aerial vehicles (UAVs).
"US Navy personnel are on the Mercer Street, assisting the vessel’s crew. The US Navy’s 5th Fleet headquarters is co-ordinating with vessel ownership regarding the type of assistance requested," the statement added.
Private maritime intelligence firm Dryad Global also referred to a drone sighting involving the vessel prior to the attack.
Iran and Israel have traded accusations of attacking each other's vessels in recent months. On Friday, Israeli Foreign Minister Yair Lapid said he had told Britain's foreign secretary of the need for a tough response to the incident.
"Iran is not just an Israeli problem, but an exporter of terrorism, destruction and instability that harms us all. The world must not be silent in the face of Iranian terrorism," Mr Lapid said.
The company which owns the Mercer Street belongs to Israeli tycoon Eyal Ofer, and released a statement saying an investigation was under way and that it was not aware of any other personnel being harmed.
The company described the attack as “piracy”, without elaborating.
The British victim worked as a guard for UK maritime security firm Ambrey, the company said.
Iran and Yemen’s Tehran-backed Houthi rebels have employed suicide drones in the past, unmanned aircraft loaded with explosives that detonate on impact with a target.
Zodiac said the ship was Japanese-owned and sailed under a Liberian flag. Britain's defence ministry had earlier described it as Israeli-owned.
Other Israeli ships have been targeted in recent months, with Israel blaming Iran for the incidents.
The British military's UK Maritime Trade Operations said an investigation was under way into the incident, which it said happened late on Thursday night, north-east of the Omani island of Masirah.
The location is more than 300 kilometres south-east of Oman’s capital, Muscat.
Earlier on Thursday, the British military group said it was investigating another unexplained incident in the same area, but did not elaborate.
“At the time of the incident the vessel was in the northern Indian Ocean, travelling from Dar es Salaam to Fujairah with no cargo on board,” Zodiac said, naming ports in Tanzania and the United Arab Emirates, respectively.
Satellite tracking data from MarineTraffic.com showed the vessel had been near where British officials said the attack occurred.
The incident took place outside Oman’s waters, according to an official quoted by the Oman News Agency.
The official at Oman's Maritime Security Centre said the air force flew sorties over the site and a naval ship was dispatched after receiving a distress signal from the vessel. However, the ship’s owners and crew said the vessel was able to proceed to its destination without further assistance.
Since former US president Donald Trump unilaterally withdrew America from the nuclear accord in 2018, there have been a series of attacks on ships in the region, with Iran the prime suspect.