The Foreign Office has summoned Iran’s charge d’affaires following the seizure of a British-flagged oil tanker in the Strait of Hormuz.
It comes as Iran directly linked the seizure of the tanker with Britain’s role in detaining a tanker carrying Iranian oil earlier this month.
A spokesman for Iran’s Guardian Council was quoted as saying “the rule of reciprocal action is well-known in international law” and that Tehran made the right decision in the face of an “illegitimate economic war and seizure of oil tankers”.
The explanation, which contrasts with a suggestion on Friday night that the Stena Impero was “violating international maritime rules” and had collided with a fishing boat, came as the UK government warned British ships to stay away from the Strait of Hormuz and described the seizure of the UK registered vessel as “unacceptable”.
Foreign Secretary Jeremy Hunt said on Saturday afternoon that he had spoken to his Iranian counterpart Mohammad Javad Zarif and expressed his “extreme disappointment” at the situation.
HMS Montrose, which is patrolling the Persian Gulf to protect shipping and earlier this month intercepted Iranian patrol boats surrounding another UK-flagged tanker, reportedly arrived minutes too late to prevent the latest incident.
Defence Secretary Penny Mordaunt described the incident – which she said happened in Omani waters – as a “hostile act”, according to Sky News.
And she said Montrose was 60 minutes away from being able to help.
Stena Bulk, which owns the Stena Impero, said the ship was in “full compliance with all navigation and international regulations” when it was seized by the Iranian Revolutionary Guard.
A second oil tanker, the Liberian-flagged Mesdar, which is managed by Norbulk Shipping UK, veered off course towards the Iranian coast after it was boarded by armed guards at around 5.30pm on Friday.
The Mesdar’s Glasgow-based operator said communication had since been re-established with the ship and the crew were unharmed. The tanker was reportedly allowed to resume navigation.
The Government’s emergency committee Cobra met on Friday night and ministers were expected to discuss the crisis further on Saturday.
Downing Street said Prime Minister Theresa May was in her constituency but was being kept informed of developments.
After the Cobra meeting, a Government spokesman said the seizure was “a clear challenge to international freedom of navigation”, adding: “As the Foreign Secretary has said, our response will be considered and robust and there will be serious consequences if the situation is not resolved.”
Former chief of defence staff Lord Richards said Britain was “pretty limited” in what military action it could take without the support of allies such as America, should economic sanctions fail to resolve the situation.
But Mr Hunt said he had spoken to US Secretary of State Mike Pompeo about the situation and President Donald Trump said America would be “working with the UK”.
He told reporters: “We will talk to the UK and we have no written agreement but we have an agreement. They’ve been a very great ally of ours.”
France and Germany joined condemnation of Iran’s actions, which have triggered concerns that it will lead to further oil price hikes amid heightened tensions in the Gulf involving Iran, the US and UK.
Fears had been growing that the Iranian authorities were trying to seize a UK ship in retaliation for the seizure of the Grace 1 tanker off the coast of Gibraltar on July 4 in an operation involving Royal Marines.
The Grace 1 was suspected of violating EU sanctions by carrying a cargo of Iranian oil destined for Syria in breach of sanctions and Mr Hunt later offered to help release the vessel if Iran guaranteed it would not breach sanctions imposed on Bashar Assad’s regime.
But Iran’s supreme leader Ayatollah Ali Khamenei called the tanker’s seizure an act of “piracy” on Tuesday and warned the UK to expect a response.
A statement from Stena Bulk said ship manager Northern Marine Management had lost contact with the crew of 23 after “unidentified small crafts and a helicopter” approached the vessel at about 4pm on Friday.
The company said the tanker was in international waters at the time but appeared to be heading north towards Iran.
Erik Hanell, president and chief executive of Stena Bulk, said: “There are 23 seafarers onboard of Indian, Russian, Latvian and Filipino nationality.
Iran’s behaviour is unacceptable and they’ve got to release the shipJohn McDonnell
“There have been no reported injuries and the safety and welfare of our crew remains our primary focus. We are in close contact with both the UK and Swedish government authorities to resolve this situation and we are liaising closely with our seafarers’ families.”
Labour shadow chancellor John McDonnell said the seizure of a British oil tanker was “unacceptable” and called for it to be released.
“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.
“The key issue now is getting people back round the table.
“All the military advisers that I’ve listened to, retired military, have been saying we’ve got to get back round the table, and we could play that role.
“The US destabilised the situation a bit, by pulling out of the agreement that we had, that we helped broker, and what we need to do now is act in the role of honest broker now.
“But Iran’s behaviour is unacceptable and they’ve got to release the ship.”