United States of America Secretary of State Mike Pompeo has blamed Iran for "unprovoked attacks" on two oil tankers in the Gulf of Oman.
Mike Pompeo said that the US had made its assessment based on intelligence about the type of weapons used.
"It is the assessment of the United States that Iran is responsible for the attacks," the US secretary of state said at a news conference in Washington.
"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."
Two oil tankers were attacked in the Gulf of Oman on Thursday, leaving one ablaze and both adrift, shipping firms said, driving oil prices as much as 4% higher over worries about Middle East supplies.
The Front Altair, carrying petrochemical feedstock, was on fire in waters between Gulf Arab states and Iran after an explosion that a source blamed on a magnetic mine. The Norwegian owner said its crew were safe.
A second Japanese-owned tanker was abandoned after being hit by a suspected torpedo, the firm that chartered the ship said. The crew were also picked up.
Thursday's attacks were the second in a month near the Strait of Hormuz, a major strategic waterway for world oil supplies.