Two vessels in the Strait of Hormuz were seized by Iranian authorities on Friday, a British official said.
Foreign Secretary Jeremy Hunt in a statement said he is "extremely concerned" by the apprehension of the two vessels, one of which is British-flagged and the other Liberian-flagged.
"Our Ambassador in Tehran is in contact with the Iranian Ministry of Foreign Affairs to resolve the situation and we are working closely with international partners," Hunt said. “These seizures are unacceptable. It is essential that freedom of navigation is maintained and that all ships can move safely and freely in the region.”
Those aboard the vessels are from "a range of nationalities," but none are believed to be British citizens, he said.
Hunt said he will soon attend an emergency government meeting to see what can be done to secure the vessels' release.
Earlier Friday, Iran's Revolutionary Guard said it had seized a U.K. oil tanker in the Strait of Hormuz, claiming the vessel was operating against “international maritime laws and regulations.”
Word of the seized Stena Impero was shared to the IRGC’s website, according to The Associated Press.
Stena Bulk, the vessel’s owner, released a statement confirming that it “was approached by unidentified small crafts and a helicopter during transit of the Strait of Hormuz” while it was navigating in international waters.
The company said they couldn’t get in touch with the Stena Impero, “which is now heading north towards Iran.”
Twenty-three people were on board the vessel and, to the company’s knowledge, no one has been hurt, it said. The crew’s “safety is of primary concern to both owners and managers.”
A U.K. government spokesperson released a statement on the matter to Fox News.
“We are urgently seeking further information and assessing the situation following reports of an incident in the Gulf,” the spokesperson said.
President Trump also reacted to the seizures while talking to reporters at the White House on Friday, condemning Iran as being "nothing but trouble." But he also expressed optimism, saying he believed the situation with Tehran would eventually work out "very nicely."
The seize comes amid growing tension in the region. Trump on Thursday said a U.S. warship destroyed an Iranian drone in the Strait of Hormuz after it threatened the ship. The Navy's USS Boxer, an amphibious assault ship, took defensive action after the Iranian aircraft closed to within 1,000 yards of the ship and ignored multiple calls to stand down, he said.
"The United States reserves the right to defend our personnel, facilities and interests and calls upon all nations to condemn Iran's attempts to disrupt freedom of navigation and global commerce," Trump said.
And last week, the British navy said it prevented three Iranian paramilitary vessels from impeding the passage of a British oil tanker in the Strait of Hormuz. Iran's Revolutionary Guard denied the allegations, saying if it had received orders to seize any ships it would have done so immediately.
In commenting on Friday's situation, National Security Council Spokesman Garrett Marquis mentioned the previous incident with the U.K. and expressed solidarity "with our allies and partners to defend our security and interests against Iran’s malign behavior."
"We are aware of reports that Iranian forces seized a British oil tanker," Marquis said. "This is the second time in just over a week the UK has been the target of escalatory violence by the Iranian regime."
Fox New's Rich Edson, Lucas Tomlinson, FOX Business' Ken Martin and The Associated Press contributed to this report.