"The Iranian government is obviously to blame for taking the tanker, it's unacceptable behaviour and we echo what the Government has said", he told PA on Saturday.
"We are aware of reports that Iranian forces seized a British oil tanker", spokesman Garrett Marquis said.
The Stena Impero was taken to Bandar Abbas on Friday night by the naval forces of Iran's Revolutionary Guards and the investigation into the accident began on Saturday, Afifipour said, according to Fars.
The Algerian state oil and gas company Sonatrach says that the Iranian coast guard forced one of its tankers to head into Iranian waters before a confrontation ended. Lord West's convoys may serve that objective by preventing further incidents. Then the United States said it had shot down an Iranian drone, which Tehran denied.
Hunt said "due process" will continue in the Grace 1 case to determine what happens to the tanker and its cargo and called for Iran to also follow legal norms.
The past three months of escalation have seen the United States and Iran come as close as ever to direct military confrontation.
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Iranian state TV said it was taken by the drone alleged to have been downed, as it flew over an American amphibious group led by the USS Boxer - the navy ship in question.
A spokesperson for the Revolution Guards said they were able to bring the Stena Impero to their shores despite "resistance and interference" from a British warship.
But the pictures are inconclusive, says the BBC's diplomatic correspondent Paul Adams.
He had said on Friday that Britain was however "not looking at military options".
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US President Donald Trump said on Friday he would talk to Britain about the seizure.
At the time Hunt spoke, Iran had at least briefly detained a second British owned ship, and Hunt said the meeting would address "what we can do to swiftly secure the release of the two vessels".
"The drone was immediately destroyed. after ignoring multiple calls to stand down", he added.
According to the operator Northern Marine the vessel was approached by helicopters and other ships.
Trump pulled the United States out of the deal a year ago and began ratcheting up sanctions against Iran.
In comments on Twitter on Saturday, Iran's Foreign Minister Mohammad Javad Zarif characterized the seizure of Iran's tanker July 4 as "piracy".
It's not the first time the U.S. and Iran have been at odds over an incident in the strategic sea passage in the Gulf.
He said it was Iran that guarantees the security of the Gulf and the Strait of Hormuz.
The semi-official Fars news agency quoted Abbas Ali Kadkhodaei, a council spokesman, as saying Saturday that "The rule of reciprocal action is well-known in worldwide law".
Britain, which remains a signatory to the nuclear accord, has figured prominently in rising US tensions with Iran ever since Royal Marines took part in the seizure of the Iranian oil tanker by Gibraltar, a British overseas territory off the southern coast of Spain.
But on that occasion, the Iranian vessels backed off when confronted by a British Royal Navy warship. The Liberian-flagged ship was later released. There have also been attacks on oil tankers in recent weeks that the USA blames on Iran - an allegation denied by the Islamic Republic.
The seven-minute video, apparently shot from high altitude, shows a convoy of ships the Guards said they were tracking as they passed through the strait.