DUBAI, United Arab Emirates - Iran's Revolutionary Guard Corps seized at least one British tanker in the Strait of Hormuz on Friday, according to Iranian state media, setting up a new showdown with the West and demonstrating Tehran's growing boldness as it seeks to challenge the United States and its allies in the strategic waterway.
A statement from the Revolutionary Guard that was read on Iranian state television said the British-flagged tanker Stena Impero had been seized in the Persian Gulf but gave no further details.
U.S. officials and shipping reports from the region indicated that a second tanker, the Mesdar, flagged in Liberia but operated by a British company, also had been seized, but that information could not immediately be confirmed.
Both tankers were seen to sharply change course and head toward Iran as they entered the Persian Gulf through the Strait of Hormuz, according to the shipping tracking service MarineTraffic.com. By early Saturday morning, the Mesdar had changed course again and appeared to have resumed its scheduled journey toward the Saudi port of Ras Tanura.
The Strait of Hormuz is the narrow waterway that controls access to the Persian Gulf, the route for a fifth of the world's tanker traffic.
The British government said it was "urgently" seeking further information about both tankers. The operator of the Stena Impero tanker, Stena Bulk and Northern Marine Management, said the vessel was in international waters when it was "approached by unidentified small crafts and a helicopter during transit of the Strait of Hormuz."
The ship diverted on a course north toward Iran, and then contact was lost, the company said.
British Foreign Secretary Jeremy Hunt said he was "extremely concerned" by the possible seizures and would be holding an urgent meeting of top members of the British government late Friday night to discuss Britain's response. He added that no British citizens were among the crew but did not identify the nationalities of those on board.
In Washington, President Donald Trump said the interception of the British ship proved his repeated assertions that Iran is "nothing but trouble."
"It goes to show you I was right," he said, adding, "it's not American, it's U.K. . . . Let's see what happens."
The apparent diversions follow Iran's threats to retaliate for the seizure of an Iranian tanker by British forces off Gibraltar in early July on suspicion of smuggling oil to Syria in violation of European Union sanctions.
Hours earlier, the Gibraltar Supreme Court granted a 30-day extension to the authorities to continue to detain the Grace 1 supertanker; that order may have triggered Iran's decision to implement the threat to retaliate by seizing a British tanker.
The interceptions signal a wider escalation by Iran in its two-month-old campaign of threats and attacks against U.S. and allied warships and commercial shipping in the vicinity of the Persian Gulf, as Tehran seeks to push back against the Trump administration's imposition of tough new sanctions. Iran has denied U.S. allegations that it is behind most of the attacks.
The new tensions coincide with the arrival in the region of U.S. naval reinforcements aimed at deterring just such attacks against international shipping. Among the U.S. warships that have arrived in the region is the USS Boxer, which brought down an Iranian drone Thursday that had approached dangerously near, according to Trump and the Pentagon.
On Friday, however, Iranian television aired footage showing drone images of warships that the broadcaster said disproved Trump's assertion that the U.S. military had destroyed an Iranian drone.
The television station said the footage was provided by the Revolutionary Guard and showed Boxer entering the Strait of Hormuz. The video was also posted by Iran's Press TV and included images taken from above what appeared to be a warship, but the veracity of the footage could not immediately be verified.
This latest spike in tensions came almost exactly a month after Iran downed a U.S. drone over the same waterway, prompting Trump to consider launching a military strike against Iran.
Trump said Thursday that Boxer destroyed the drone after it approached within 1,000 yards of the amphibious assault ship. The Pentagon confirmed that the incident took place, saying the drone was brought down around 10 a.m. Thursday.
Iran denied, however, that any encounter had occurred between one of its drones and a U.S. warship, insisting that all its drones were accounted for.
"We have not lost any drone in the Strait of Hormuz nor anywhere else," Deputy Foreign Minister Abbas Araghchi said on his Twitter account. He suggested that the United States may have shot down one of its own drones "by mistake."
Iran's top military spokesman also said there had been no incident involving any Iranian drone.
"All Iranian drones that are in the Persian Gulf and the Strait of Hormuz, including the one which the U.S. mentioned, after carrying out scheduled identification and control missions, have returned to their bases," said Brig. Gen. Abolfazl Shekari, according to Iran's Tasnim News Agency.
Boxer is part of a U.S. amphibious force that arrived in the region this week and includes more than 2,000 Marines from the 11th Marine Expeditionary Unit. The Trump administration has accused Iran of being behind a string of incidents, including attacks and harassment against commercial shipping, that have contributed to the rising tensions in the region as the United States squeezes Iran with tighter sanctions.
Iran has denied involvement. On Thursday, however, Iran acknowledged that it had seized a United Arab Emirates-based ship that was reported missing last weekend. The Panama-registered Riah was detained because it was suspected to be involved in smuggling, Iran's Revolutionary Guard announced Thursday.
The State Department and Pentagon were to hold a meeting with diplomats Friday to discuss the need for a coalition to protect maritime security around the Strait of Hormuz.
"A multinational effort is needed to address this global challenge and ensure the safe passage of vessels," the State Department said in a statement.
A U.S. official, speaking on the condition of anonymity because of the sensitivity of the situation, said the U.S. military has surveillance aircraft in the region watching what is happening. Naval Forces Central Command, which oversees U.S. military operations in the region, has been in contact with commercial U.S. ships in the region.
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The Washington Post's Karla Adam in London and Brian Murphy and Carol Morello in Washington contributed to this report.
This article was written by Liz Sly, a reporter for The Washington Post.