- Video report by ITV News International Affairs Editor Rageh Omaar
The United States has blamed Iran for attacks on two oil tankers in the Gulf of Oman.
Secretary of State Mike Pompeo said the United States believes that the attacks on the ships are part of a “campaign” of “escalating tension” by Iran and a threat to international peace and security.
The attacks happened near the strategic Strait of Hormuz and were described by Iran as "suspicious".
A South Korean company confirmed that all the 23 crew aboard one of the tankers had been rescued by one of its cargo vessels sailing in the area.
Meanwhile, Iranian state television reported that 44 sailors from the two tankers had been transferred to an Iranian port in the southern province of Hormozgan.
The Navy and the ship's owners offered no explanation on what weapon caused the damage to the MT Front Altair - a Marshall Islands-flagged crude oil tanker - and the Kokuka Courageous, though all say the ships had been targeted in an attack.
Speaking in Washington on Thursday, Mr Pompeo said a US assessment of Iran's responsibility, which forced the evacuation of the crews in international waters, was based in part on intelligence as well as the expertise needed to carry out the operation.
It was also based on a recent series of incidents in the region that the US also blames on Iran, including a similar attack on tankers in the area in May and the bombing of an oil pipeline in Saudi Arabia by Iranian-backed fighters, he said.
"Taken as a whole these unprovoked attacks present a clear threat to international peace and security, a blatant assault on the freedom of navigation and an unacceptable campaign of escalating tension by Iran," Mr Pompeo said.
The US plans to raise the attacks at the UN Security Council later on Thursday.
Mr Pompeo also said the US would defend its forces and interests in the Middle East but gave no details on any immediate plans.
He continued that Iran had attempted the covert deployment of small boats capable of launching missiles, in an apparent description of the threat that prompted the deployment.
Despite the US's allegations, no one has claimed responsibility or explained how the tankers were attacked, but Iranian foreign minister Mohammad Javad Zarif described the incident as "suspicious".
Tensions between Iran and the United States have been growing since President Donald Trump last year withdrew from an international agreement aimed at restricting Iran's nuclear program and re-instated economic sanctions that have had a devastating effect on the Iranian economy.
In May, the US rushed an aircraft carrier strike group and other military assets to the Persian Gulf region in response to what it said were threats from Iran.
Benchmark Brent crude oil spiked 4% in trading following the reported attack to more than 62 dollars a barrel, according to early market figures.
The timing of Thursday's reported attack was especially sensitive as Japanese Prime Minister Shinzo Abe was visiting Iran on a high-stakes diplomacy mission.