Iran has seized a commercial ship with links to Israel as it passed through the Strait of Hormuz early on Saturday.
The MSC Aries was boarded by Iranian special forces about 50 miles (80km) off the coast of the United Arab Emirates, a statement from the vessel's operator MSC said.
Footage obtained by Reuters news agency appeared to show troops rappelling onto the vessel from a helicopter.
The Portuguese-flagged ship is linked to Israeli billionaire Eyal Ofer.
The incident comes amid heightened expectation of an Iranian attack on Israel after an airstrike destroyed Iran's consulate in Damascus at the start of April. Israel said on Saturday Iran would bear the consequences for choosing to escalate the situation any further.
Tracking data last showed the MSC Aries off the coast of the UAE, heading towards the Strait of Hormuz over 18 hours ago. It then appeared to turn off its tracking data, which is common for Israeli-affiliated ships in the region.
The UK's Maritime Trade Operations agency confirmed the boarding in a statement. It made no mention of Iranian involvement, instead stating that the ship had been seized by "regional authorities" off the coast of Fujairah in the UAE.
However, Iranian media has been quick to trumpet the involvement of the country's special forces in the attack.
The country's state news agency, Irna, said the naval branch of the Islamic Revolutionary Guards Corps (IRGC) had seized the MSC Aries as it was "linked to Israel". It added that the ship was in the process of being transported to Iranian waters.
In video footage, troops could be seen rappelling onto the vessel from a helicopter hovering overhead. A crew member could be heard shouting: "Don't come out."
In the video, one commando could also be seen kneeling to provide cover fire as other troops boarded the ship. According to MSC there were 25 crew members onboard at the time of the seizure.
White House National Security Council spokesperson Adrienne Watson said the crew is comprised of Indian, Filipino, Pakistani, Russian and Estonian nationals.
"We call on Iran to release the vessel and its international crew immediately," Ms Watson said in a statement.
"Seizing a civilian vessel without provocation is a blatant violation of international law, and an act of piracy by the Islamic Revolutionary Guards Corps, a designated Foreign Terrorist Organization.
"It must be condemned unequivocally, and we will work with our partners to hold Iran to account for its actions."
Officials in Tehran have yet to comment on the seizure.
The ship is managed by MSC, which leases the vessel from Gortal Shipping Inc - a company affiliated with Mr Ofer's Zodiac Maritime.
In response to the attack, Israeli Foreign Minister Israel Katz called on the European Union "to immediately declare the Iranian Revolutionary Guards corps as a terrorist organization and to sanction Iran" in a post on X, formerly known as Twitter, saying that the cargo ship belongs to an EU member.
US warns of impending Iran attack
Since 2019 Iranian forces have carried out a series of ship seizures in the region and the attack comes amid mounting tensions between Iran and Israel.
Ever since the lethal 1 April attack on the Iranian consulate building in Damascus, which killed a senior IRGC commander, Iran has vowed to strike back at Israel, which it blames for the attack.
While Israel has declined to comment on the attack, US officials have repeatedly warned that they expect Iran to attack Israel "sooner than later".
On Friday, President Joe Biden warned Tehran against an attack on Israel.
"We are devoted to the defence of Israel. We will support Israel," Mr Biden said. "We will help defend Israel and Iran will not succeed."
A spokesperson for Israel's military said on Saturday that Iran would "bear the consequences for choosing to escalate the situation any further".
Meanwhile, the military announced a nationwide halt to educational activities, amid ongoing concerns over the potential of an attack by Iran. The suspension will begin at 23:00 local time on Sunday.
Officials also announced a limit on public gatherings of 1,000 people.
