A British crew member was among two workers killed in an attack on an oil tanker in the Arabian Sea.
The Mercer Street petroleum products tanker was targeted off the Omani coast, with a Romanian worker also killed, the vessel's managing company has confirmed.
The firm - part of Israeli billionaire Eyal Ofer's Zodiac Group - said it is investigating "a suspected piracy incident" on board the ship.
However, the Royal Navy's Maritime Trade Operations denied the attack involved piracy but confirmed a probe was underway to understand what happened.
The tanker was reported to be travelling from Dar es Salaam, Tanzania's largest port, to Fujairah in the UAE with no cargo on board.
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And it was attacked northeast of the island of Masirah, over 135km southeast of Muscat.
"We are not aware of harm to any other personnel," the company, which is based in the UK, said in a statement.
"Our primary concern remains the safety and wellbeing of everyone on board and all those affected by the situation."
"Details of the incident are still being established and an investigation into the incident is currently underway. We continue to work closely with the UKMTO and other relevant authorities."
Israeli officials are yet to confirm the incident.
It remains unclear how the medium-sized Japanese-owned tanker was attacked or by who.
While how many crew were on board and their nationalities is also not been released.
It comes amid heightened tensions between Israel and Iran as negotiations remain stalled over Tehran's nuclear deal with world powers.
Other Israel-linked ships have been targeted in recent months, with the government blaming the Islamic Republic.
While Israel itself has been suspected in multiple attacks against Iran's nuclear programme.
Earlier on Thursday, the British military group said it was also investigating a separate incident in the same area, but gave no further details.
A spokesperson for the Ministry of Defence said: "We are aware of reports of an attack on a merchant vessel off the coast of Oman. UK military headquarters in the region are currently conducting investigations."
A second Zodiac statement added: "We can confirm that there has been a suspected piracy incident onboard the product tanker M/T Mercer Street.
"The ship is a Japanese owned vessel managed by our UK based Zodiac Maritime Office. 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.
"We are in coordination and liaising with the UK MTO and other relevant authorities."
