LONDON -- British Prime Minister Theresa May chaired an emergency security session on Monday to discuss how to respond to Iran's seizure of a British-flagged tanker in the Strait of Hormuz.
The meeting of security ministers and officials discussed how to secure shipping in the sensitive region, which is vital to the world's oil supply.
Foreign Secretary Jeremy Hunt plans to brief Parliament on the Friday seizure of the Stena Impero tanker and its crew of 23, now in a heavily guarded Iranian port.
Iran released new video showing the ship's crew for the first time on Monday, an apparent attempt to show they were unharmed. None of the 23 are British nationals. The crew is mostly Indian, and includes Filipino, Russian and Latvian nationals.
May's official spokesman, James Slack, said Iran seized the ship under false and illegal pretenses and it needs to release it and its crew immediately. Iranian officials have suggested the seizure was in response to Britain's role in seizing an Iranian oil tanker two week earlier.
Slack said giving an individual naval escort to all U.K.-flagged ships is not an option because of the volume of traffic. But he denied cuts have made the Royal Navy too small.
"We have the largest military budget in Europe, and we are investing in a world-class Royal Navy," he said.
Britain is considering a number of options to raise the economic and diplomatic pressure on Iran but officials say military operations are not being considered at the moment. Britain is also seeking support from key European allies in an effort to keep the Strait of Hormuz open to shipping.
One-fifth of all global crude exports passes through the narrow waterway, which lies between Iran and Oman. Maritime industry publication Lloyd's List said there are currently no U.K.-flagged ships heading to the Persian Gulf and eight U.K.-flagged vessels anchored there after a government advisory to such vessels to avoid the Strait of Hormuz.
The tanker crisis is unfolding in the final days of May's leadership. The Conservative Party plans to name her successor Tuesday, and the new prime minister -- either front-runner Boris Johnson or Hunt -- is expected to take office Wednesday.
Friday's seizure of the Stena Impero came amid heightened tensions between the U.S. and Iran stemming from President Donald Trump's decision last year to pull the U.S. from Iran's nuclear accord with world powers and reinstate sweeping sanctions on Iran.
Iranian officials say the seizure of the British oil tanker was a justified response to the Royal Navy's role impounding its Grace 1 supertanker with some 2 million barrels of crude off the coast of Gibraltar, a British overseas territory located on the southern tip of Spain.
Iran's government spokesman Ali Rabiei said Monday that there are diplomatic solutions to the current crisis, but he also defended Iran's actions.
"When you illegally seize a ship in Gibraltar... we don't deem it as necessary to show tolerance," he said. "Some countries have asked for the immediate release of the British tanker. Well, we ask those countries to make the same request to Britain first."
Britain says it acted lawfully off the Gibraltar coast to prevent illegal oil shipments to Syria that would have violated European Union sanctions while Iran broke international maritime law by forcing the Stena Impero to change course and go to Iran.
Britain says the tanker was in Omani waters at the time, which Iran disputes.
In the newly released video on Monday, the Stena Impero crew is seen dressed in red uniforms and seated around a table onboard as an unidentified Iranian man is heard thanking them for their co-operation. A cameraman is heard telling them not to look at the camera.
It wasn't clear if the crew was under duress to take part in the filming.
Other choreographed shots show a man checking on the ship, the crew sharing a laugh and talking next to a coffee machine inside the ship. The crew's chefs are seen preparing food. Another video released by Iran's state broadcaster shows Iran's flag hoisted on the ship's bridge.
Meanwhile, officials in Gibraltar say the ship's crew has been kept on board the vessel since its seizure July 4. Four Indian crewmembers, including the ship's captain, were arrested, but not charged, and were then bailed. Gibraltar says they have been in contact with their families are receiving consular support. The crew is comprised of Indian, Pakistani and Ukrainian nationals.
As the nuclear deal between Tehran and world powers unravels, the U.S. has expanded its military presence in the region, while Iran has begun openly exceeding the uranium enrichment levels set in the accord to try to pressure Europe into alleviating the pain caused by the sanctions.
European nations are trying to save the nuclear deal and have tried to come up with ways to keep trading with Iran but have run smack into Trump's sanctions, which also target Iranian oil exports.
Britain is adding to its military profile in the region but it does not have the naval resources that would be needed to protect all of its shipping interests. More than 400 transits through the Strait of Hormuz were made last year by U.K. associated ships.
On Sunday, an audio released by maritime security risk firm Dryad Global showed that a British frigate was too far away from the targeted tanker to keep it from being diverted into an Iranian port, despite U.K. efforts to keep it from being boarded.
In the audio, a British naval officer from the HMS Montrose patrolling the area is heard telling the Iranian patrol boat: "Please confirm that you are not intending to violate international law by unlawfully attempting to board the MV Stena."
His words did nothing to deter the Iranians.
Iran's Revolutionary Guard released video of the seizure, showing Iranian commandos in black ski masks and fatigues rappelling from a helicopter onto the vessel.
Associated Press writer Aya Batrawy from Dubai, United Arab Emirates, contributed to this report