The US has blamed Iran for an attack on two oil tankers in the Gulf of Oman that left one ablaze and both adrift.
"The Islamic Republic of Iran is responsible for the attacks that occurred in the gulf of Oman today," US Secretary of State Mike Pompeo said.
"This assessment is based on intelligence, the weapons used, the level of expertise needed to execute the operation, recent similar Iranian attacks on shipping and the fact that no proxy group operating in the area has the resources and proficiency to act with such a high degree of sophistication."
The targeted ships are owned by Norway and Japan.
Pompeo has called an urgent meeting of the United Nations Security Council.
UN Secretary-General Antonio Guterres strongly condemned the attacks, warning that the world cannot afford "a major confrontation in the Gulf region".
"I strongly condemn any attack against civilian vessels. Facts must be established and responsibilities clarified," he told a meeting of the UN Security Council on cooperation between the United Nations and the League of Arab States on Thursday.
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The attacks were the second in a month near the Strait of Hormuz, a major strategic waterway for world oil supplies.
The US and Saudi Arabia blamed Iran for last month's attacks using limpet mines on four tankers off the coast of the United Arab Emirates, a charge Tehran denies.
Arab League Secretary-General Ahmed Aboul Gheit called on the UN Security Council to act against those responsible to maintain security in the Gulf region.
"Some parties in the region are trying to instigate fires in the region and we must be aware of that," he told the 15-member council, without specifically naming anyone.
No one has claimed responsibility for the strikes.
Meanwhile, Russia has warned against rushing to attribute blame for the suspected attack, saying the incident should not be used to stoke tensions with Tehran.
"I would take the opportunity to warn against hasty conclusions, against attempts to lay the blame at the door of those we don't like," Russia's RIA news agency quoted Russian Deputy Foreign Minister Sergei Ryabkov as saying.
"Lately we have been seeing a strengthening campaign of political, psychological and military pressure on Iran. We wouldn't want the events that have just happened, which are tragic and shook the world oil market, to be used speculatively to further aggravate the situation in an anti-Iranian sense," Ryabkov was quoted as saying.
Russia and Iran share common interests in the Middle East. Moscow has spoken out against Washington's decision to unilaterally withdraw from a deal with Tehran on its nuclear programme and impose sanctions.
Reuters / Newshub.