Britain says three Iranian boats "attempted to impede" a British oil tanker in the strategic Strait of Hormuz, in a move that followed threats from Tehran that London would face consequences for the seizure of an Iranian supertanker last week.
"Contrary to international law, three Iranian vessels attempted to impede the passage of a commercial vessel, British Heritage, through the strait of Hormuz," said a government statement released on July 11.
The British warship, HMS Montrose, was "forced to position herself between the Iranian vessels and British Heritage and issue verbal warnings to the Iranian vessels, which then turned away," the statement said, urging Iran to "de-escalate the situation in the region."
Iran’s Islamic Revolutionary Guards Corp (IRGC) denied trying to stop the British tanker, the semiofficial Fars news agency reported on July 11.
Iranian Foreign Minister Mohammad Javad Zarif dismissed the British report as being intended to "create tension" and "worthless," according to Fars.
The incident came almost a week after British Royal Marines boarded an Iranian tanker, the Grace 1, off the coast of Gibraltar and seized it over suspicions it was breaking sanctions by taking oil to Syria.
Gibraltar police said on July 11 that the captain and chief officer of the seized Iranian tanker were arrested.
"This follows a protracted search of the vessel where documents and electronic devices have been seized and examined," police said in a statement.
Gibraltar police are interviewing both men, who have "been accorded their legal entitlements and access to consular representation," the statement added.
Iran has demanded the immediate release of the oil tanker. An IRGC commander threatened on July 5 to seize a British ship in retaliation.
Admiral Ali Fadavi, an IRGC commander, said on July 11 that Britain and the United States would regret detaining Iran's oil tanker.
"Their action was very silly and they will certainly regret it," he said, according to the hard-line Tasnim news agency. “Our reciprocal action will be announced."
On July 10, Iranian President Hassan Rohani warned that Britain would face "consequences" over the seizure of the Iranian tanker.
Earlier, U.S. media reported that five armed Iranian boats attempted to seize a British tanker in the strategic Strait of Hormuz but were driven off by a Royal Navy vessel.
The CNN news channel, citing two U.S. officials, reported late on July 10 that the Iranians ordered the British Heritage oil tanker crossing the strait to change course and stop in Iranian territorial waters nearby.
But the incident ended when the HMS Montrose, which was acting as an escort for the tanker, pointed its guns at the Iranian boats as a warning, forcing them to back off, CNN said.
Russia's Deputy Foreign Minister Sergei Ryabkov, quoted by the RIA Novosti news agency, said on July 11 that the "situation is very concerning" and blamed the incident on "Washington's deliberate, premeditated course to exacerbate tensions."
U.S. President Donald Trump threatened on July 10 to ratchet up sanctions on Iran and again denounced the 2015 nuclear deal Iran signed with world powers as the UN nuclear watchdog held an emergency meeting on Tehran's breach of the deal.
"Sanctions will soon be increased, substantially!" Trump said on Twitter.
Trump spoke with Israeli Prime Minister Benjamin Netanyahu, a staunch critic of the nuclear deal, about national-security issues, including Iran on July 10, the White House said.
"The two leaders discussed cooperation between the United States and Israel in advancing shared national-security interests, including efforts to prevent Iran’s malign actions in the region," White House spokesman Judd Deere said in a statement on July 11.
Trump last year pulled the United States out of the deal, which offered Tehran sanctions relief in exchange for significant curbs on its sensitive nuclear activities.
Iran had been complying with the deal, but over the weekend it increased its uranium enrichment beyond limits set in the accord in an attempt to pressure European countries to find a way around U.S. sanctions.