Saudi Arabia said two of its oil tankers were sabotaged off the coast of the United Arab Emirates and described it as an attempt to undermine the security of crude supplies amid tensions between the United States and Iran.
One of the ships was en route to pick up Saudi oil to take to the United States, Saudi Energy Minister Khalid al-Falih said on Monday.
The announcement by Falih came as the UAE's regional allies condemned the reported sabotage on Sunday of four ships off the coast of the port city of Fujairah.
Emirati officials have declined to elaborate on the nature of the sabotage to the ships or say who might have been responsible.
The UAE identified the vessels as very large crude carrier (VLCC) tanker Amjad and crude tanker Al Marzoqah, both owned by Saudi shipping firm Bahri. The other two were UAE-flagged fuel bunker barge A Michel and Norwegian-registered oil products tanker MT Andrew Victory.
The reports come as the US warned ships that "Iran or its proxies" could be targeting maritime traffic in the region, and as the US is deploying an aircraft carrier and B-52 bombers to the Gulf to counter what it called "threats from Tehran".
Falih said the attack did not cause any casualties or an oil spill but inflicted significant damage to the Saudi vessels' structures. He said it aimed to undermine maritime freedom and the security of oil supplies to consumers worldwide.
"The international community has a joint responsibility to protect the safety of maritime navigation and the security of oil tankers, to mitigate against the adverse consequences of such incidents on energy markets and the danger they pose to the global economy," he said.
The attacks occurred near the UAE's Fujairah emirate, one of the world's largest bunkering hubs lying just outside the Strait of Hormuz.
Thome Ship Management said its Norwegian-registered oil products tanker MT Andrew Victory was "struck by an unknown object".
UAE says four ships subjected to 'sabotage' off east coast
Iran's foreign ministry called the incidents "worrisome and dreadful" and asked for an investigation.
Ministry spokesman Abbas Mousavi also warned against any "conspiracy orchestrated by ill-wishers" and "adventurism by foreigners" to undermine the maritime region's stability and security.
The United States has limited information as yet about who may have been responsible for the attacks, said a US official familiar with American intelligence on the incident, who spoke to Reuters news agency on condition of anonymity.
Britain's Foreign Minister Jeremy Hunt also warned of the risks of "a conflict happening by accident" with an unintended escalation between Washington and Tehran over an unravelling nuclear deal.
On Monday, US President Donald Trump warned that it would be mistake for Iran to try anything against the United States.
Tensions have risen in the year since Trump withdrew the US from the 2015 nuclear deal between Iran and world powers, restoring US sanctions that have pushed Iran's economy into crisis. The United States said it wanted to reduce Iran's oil exports to zero.
Last week, Iran warned it would begin enriching uranium at higher levels in 60 days if world powers failed to negotiate new terms for the deal.