US investigators believe Iran or groups it supports used explosives to damage four ships off the United Arab Emirates (UAE) on Sunday, media reports say.
Military experts were reportedly sent to investigate the incident and found a large hole in each of the tankers.
No evidence has emerged to show that Iran was involved. The affected countries are yet to assign blame.
The incident has increased tensions between Iran, which borders the nearby Strait of Hormuz, and the US.
About a fifth of oil that is consumed globally passes through the strait. Last month, Iran threatened to “close” it if it was prevented from using the waterway.
This followed a US decision to end exemptions from sanctions for major importers of Iranian oil.
The team of US military investigators discovered large holes in all four of the affected ships and believe they were caused by explosive charges, the Associated Press reports, quoting an unnamed official. They did not explain how the damage was linked to Iran.
CBS carried a similar report quoting unnamed US officials.
Few details have been released about the incident, which is said to have taken place at about 06:00 (02:00 GMT) on Sunday within UAE territorial waters in the Gulf of Oman, east of the emirate of Fujairah.
