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The US and its allies are running near-continuous surveillance flights close to an oil tanker in the north Atlantic with links to Russia, Venezuela and Iran, amid reports that Moscow has sent a submarine to escort the vessel towards its territory.
Multiple flights from US bases on Iceland and by RAF Rivet Joint and P8 Poseidon planes from the UK, which are capable of helping to spot submarines, have been observed in the past 24 hours flying over the tanker.
The Wall Street Journal reported overnight that the Russian navy has deployed a submarine to escort the tanker, now known as the Marinera, citing US officials.
The presence of a Russian submarine, if confirmed, would heighten the stakes of any confrontation in the north Atlantic.
Video footage and radar satellite imagery suggest the empty oil tanker, which the US has previously attempted to seize, is also being shadowed by another vessel as it attempts to pass through the gap between Iceland and northern Scotland.
Russian state media has posted footage it claims was taken from the deck of the Marinera showing another ship within visual range. The FT has been unable to verify the low-quality footage, but it appears to show a US Coast Guard vessel.
On Tuesday evening, the Marinera was overflown by a European Space Agency Sentinel-1 satellite, which takes satellite images.
Its imagery confirms the location of the ship, and also reveals another large vessel sailing 1.75 nautical miles to its south. This second ship was not broadcasting its position or identity, but its radar shadow is consistent with that of US Coast Guard ships such as its 127m-long Legend-class cutters.
The US could try to seize the vessel as it passes Scotland on the way to Russia, with reports of a build-up of military equipment of the kind often used by special forces at US bases in the UK, including Black Hawk helicopters.
On Wednesday morning, US air force tankers, which can refuel other military aircraft in flight, broadcast position data that put them on course for the mid-Atlantic.
The heightened military activity in the Atlantic comes at a delicate time in international relations following the US’s capture of former Venezuelan president Nicolás Maduro, and as western powers push for a peace agreement between Russia and Ukraine.
The US Coast Guard attempted to seize the Marinera tanker, which was previously called the Bella 1, near the Caribbean in December as Washington was beginning a wider blockade of the country’s oil exports.
The US cited the tanker’s ties to Iranian oil shipments and lack of proper flag registration as grounds for seizure.
The Marinera, which had been travelling to Venezuela from Iran, fled back into the Atlantic.
Under the laws of the sea, warships are allowed to board suspected stateless vessels. But the tanker was sold to a Russian company while at sea, registered as Russian-flagged and changed its name.
Any attempt to seize the vessel would be likely to further strain western ties with Russian President Vladimir Putin amid negotiations over a peace deal with Ukraine.
Such a move could also raise questions over UK involvement in supporting the US, with Prime Minister Sir Keir Starmer under pressure to comment on whether he believes the US intervention in Venezuela was illegal under international law.
A UK Ministry of Defence spokesperson said that “as routine, we do not comment on the operational activity of other nations, including third party use of UK bases”.
“The US is the UK’s principal defence and security partner. The depth of our defence relationship with the US remains an essential part of our security,” the spokesperson added.