July 19 (UPI) -- Iranian officials seized two British-affiliated tankers Friday in the Strait of Hormuz, the British foreign secretary confirmed.
Details about the seizure of the Liberian-flagged, British-owned MV Mesdar tanker were less clear.
"I am extremely concerned by the seizure of two naval vessels by Iranian authorities in the Strait of Hormuz," British Foreign Secretary Jeremy Hunt said.
He said he planned to attend a Cabinet meeting to secure the release of the two vessels. The British ambassador to Iran was working with the Iranian Ministry of Foreign Affairs to resolve the situation.
"These seizures are unacceptable," Hunt said. "It is essential that freedom of navigation is maintained and that all ships can move safely and freely in the region."
The Stena Impero's owners, Stena Bulk, and managers, Northern Marine, issued a statement saying the vessel was approached by unidentified small watercraft and a helicopter while in international waters.
"We are presently unable to contact the vessel which is now heading north towards Iran," the statement said.
The owners said there were 23 personnel on board the ship at the time it was seized.
"There have been no reported injuries and their safety is of primary concern to both owners and managers," the statement said.
President Donald Trump issued a warning to Iran on Friday, one day after he said the USS Boxer brought down an Iranian drone for coming within 1,000 yards of the vessel. Chief Pentagon spokesman Jonathan Hoffman confirmed the Navy "took defensive action" against the drone.
"We have the greatest ships -- the most deadly ships, we don't want to have to use them," he told reporters at the White House. "We hope for their sake they don't do anything foolish. If they do, they will pay a price like nobody's ever paid."
Iranian Deputy Foreign Minister Seyyed Abbas Araqchi said Tehran is not missing a drone "in the Strait of Hormuz nor anywhere else."
Tensions between the United States and Iran have risen for months, and the conflict deepened after an attack on two tankers in the Gulf of Oman the United States blamed on Tehran.
Tensions first began to escalate following the Trump administration pulling out of the 2015 nuclear deal, citing it was "defective at its core."
On Friday, Trump said he planned to talk with British officials about the seizures.