Japanese tanker damaged near Oman target of a terrorist attack.
Remains of home-made explosives had been found on the hull of the M Star, which was damaged in July while travelling from Qatar to Japan, the United Arab Emirates state-run news agency reports.
An al-Qaeda-linked group has claimed responsibility.
The ship's crew reported an explosion shortly after midnight on July 28. One person was injured.
The attack was reportedly an amateur operation using crude homemade explosives which did comparatively little damage.
"UAE explosives experts who collected and examined samples found a dent on the starboard side above the water line and remains of home-made explosives on the hull," the report said.
"Probably the tanker had encountered a terrorist attack from a boat loaded with explosives," the source was quoted as saying.
The ship's owner, Mitsui OSK, said it could not confirm the reports. Japanese Foreign Minister Katsuya Okada said the government was aware of the report but was yet to confirm its details, the Agence France Presse news agency said.
It is in marked contrast to the well-planned al-Qaeda attack on the USS Cole in Aden in 2000 which blasted a hole in the warship and killed 17 US sailors, and a further al-Qaeda attack on the French operated tanker Limburg off Yemen in 2002.
An estimated 40 per cent of the world's crude oil is exported through the narrow strait between Oman and Iran, where the attack took place.