The United Arab Emirates has told the UN Security Council that a "state actor" was most likely behind attacks on four tankers off its coast.
The May 12 attacks bore the hallmarks of a "sophisticated and coordinated operation," according to its report.
The UAE did not say who it thought was behind the attacks, which also targeted vessels from Saudi Arabia and Norway.
The US has accused Iran of being behind the attacks, but Tehran has denied this and called for an investigation.
The attacks took place on 12 May, within UAE territorial waters east of the emirate of Fujairah, just outside the Strait of Hormuz, reports the BBC.
The UAE authorities said four ships were targeted in a "sabotage attack".
There were no casualties but Saudi Arabia said two of its ships had suffered "significant damage".
Another tanker was Norwegian-registered, while the fourth was UAE-flagged.
US National Security Adviser John Bolton, a long-time advocate for regime change in Tehran, said it was "clear" Iran was behind the attack.
The US sees the attacks as part of a wider "campaign" against it and its allies.
The Iranian foreign ministry branded the accusation "ludicrous".
What's the latest?
The new UAE-led probe found a "high degree of sophistication" behind the attacks.
"The attacks required the expert navigation of fast boats" which "were able to intrude into UAE territorial waters," the report stated.
Divers were used to attack the ships using limpet mines in order to cause damage but not cause a major explosion, the presentation stated.
What is behind the heightened US-Iran tensions?
The tensions began rising at the start of May, when Washington ended exemptions from sanctions for countries still buying from Iran. The decision was intended to bring Iran's oil exports to zero, denying the government its main source of revenue.
US President Donald Trump reinstated the sanctions a year ago after abandoning the landmark 2015 nuclear deal that Iran signed with six nations - the five permanent members of the UN Security Council and Germany.
Iran has now announced it will suspend several commitments under the deal.
