British armed forces played a behind-the-scenes role in a high-stakes operation that saw the United States seize a Russian-flagged oil tanker in the North Atlantic, the Ministry of Defence has confirmed.
The vessel, Marinera, previously known as Bella 1, was intercepted by the US Coast Guard on Wednesday while sailing through waters between Scotland and Iceland. The tanker is accused of being part of a so-called “shadow fleet” used to transport sanctioned oil linked to Venezuela, Russia and Iran.
According to the MoD, the UK was asked to assist the operation, deploying RAF surveillance aircraft alongside the Royal Navy support ship RFA Tideforce. British personnel did not take part in boarding the vessel, which was carried out by US forces.
Defence Secretary John Healey told MPs the operation was conducted “in full compliance with international law” and formed part of a broader effort to counter illicit maritime activity.
“We will not stand by as malign activity increases on the high seas,” Healey said, describing the action as part of the government’s stepped-up response to vessels used to evade international sanctions.
The Marinera has been under US sanctions since 2024 and is alleged to have transported more than 7.3 million barrels of oil on behalf of Iran, with proceeds used to fund terrorism and regional instability. Healey said such shadow fleets were also “vital to Putin’s illegal invasion of Ukraine”.
The tanker had been pursued by US authorities for weeks. In an earlier attempt to seize it in the Caribbean, the vessel abruptly changed course, switched its name, and re-registered under the Russian flag while at sea. It also allegedly turned off its transponders in an effort to evade tracking.
In a statement, the MoD said the ship was additionally assessed to have links to illegal activity connected to Lebanon-based militant group Hezbollah.
The US military’s European Command publicly thanked the UK for its “unwavering support”, while Downing Street confirmed that Prime Minister Sir Keir Starmer discussed the joint operation with US President Donald Trump during a phone call on Wednesday evening.
That call also touched on Ukraine, recent US action in Venezuela, and Greenland, an increasingly sensitive diplomatic issue after Trump repeated threats to annex the territory. Sir Keir has insisted that only Greenland and Denmark should decide the island’s future.
Russia has condemned the seizure, with Moscow’s transport ministry claiming the tanker had been granted “temporary permission” to fly the Russian flag and warning that no state had the right to use force against properly registered vessels. It demanded US authorities ensure Russian crew members were treated correctly and allowed to return home.
Reports suggesting Russia had deployed a submarine to protect the tanker could not be substantiated, and US forces boarded the ship without resistance.
The operation coincided with the US seizure of a second tanker, the M/T Sophia, in the Caribbean. US officials said both vessels had either recently docked in Venezuela or were en route there.
Under international maritime law, experts note that stateless or falsely flagged vessels can be lawfully boarded.
Shadow fleets, often made up of ageing tankers using fake names and flags, are increasingly used by sanctioned states to move oil covertly. Financial intelligence firm S&P Global estimates that one in five oil tankers worldwide may now be involved in sanctions evasion.
