Two crew members, a Briton and a Romanian, were killed when a petroleum products tanker managed by Israeli-owned Zodiac Maritime came under attack on Thursday off Oman's coast, the company said on Friday.
London-based Zodiac said on its website that the attack in the Arabian Sea on the Mercer Street, a Liberian-flagged Japanese-owned ship, was still being investigated.
Earlier on Friday it had described the incident as suspected piracy but the United Kingdom Maritime Trade Operations (UKMTO), which provides maritime security information, says it was not piracy.
"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," said Zodiac, which is owned by the wealthy Israeli Ofer family.
Reuters quoted it as saying that it was "not aware of harm to any other personnel" than the British and Romanian crew members who were killed.
The UKMTO said the vessel was about 152 nautical miles (280 km) northeast of the Omani port of Duqm when it was attacked. It gave no more details on the type of vessel, any cargo, to whom it belonged or about possible casualties.
Zodiac said the ship was now sailing under the control of its crew and own power to a safe location with a US naval escort.
In an advisory note, UKMTO said it had been informed that regional search and rescue authorities and coalition forces have been tasked to assist the vessel.