International investigators believe last month’s attacks on oil tankers in a United Arab Emirates port were led by a foreign state using divers on speed boats who planted mines on the vessels.
They did not name Iran, which the US has blamed for the attacks.
United Nations ambassadors from the Emirates, Saudi Arabia and Norway were given the details in a closed meeting with UN Security Council members on Thursday.
Four tankers from those countries were hit on May 12 off the Emirati coast.
US national security adviser John Bolton has said Iran is responsible for the attacks.
On Thursday, the Saudi ambassador to the UN, Abdallah Al-Mouallimi, speaking only for his country, said Saudi Arabia also blamed Iran for the sabotage.
Scientific and naval experts conducted the probe, analysing tanker debris, radar data and the precisely placed explosive charges.
Meanwhile, the top commander of US forces in the Middle East says Iran appears to have decided to “step back and recalculate” in response to a US military buildup in the Persian Gulf area.
Marine General Frank McKenzie says it is too early to conclude Iran has abandoned plans for potential attacks against American interests that prompted the buildup last month.
He told reporters on Thursday that he was assessing Iran’s stance. He said he would not rule out requesting more forces to bolster American defences.
McKenzie said Iran and its proxies posed what he called an “advanced and imminent” threat to US forces when he asked on May 5 for authority to accelerate the deployment of an aircraft carrier and send four strategic bombers to the Gulf area.