British armed forces ‌have intercepted a Russian shadow fleet oil ​tanker attempting to pass through the English Channel.

The vessel Smyrtos was boarded by ​Royal Marine commandos and specially trained law enforcement ⁠officers on Sunday, ‌Britain’s ‌ministry ​of defence said in a statement.

The vessel will ⁠be ​held and monitored ​off the south coast of England as investigations ‌continue, the statement said, ​adding that enforcement action in Britain’s ⁠territorial waters ⁠was ​carried out in accordance with domestic and international law.

British prime minister Keir Starmer said he had directed the interception.

“This successful operation delivers yet ‌another blow to Russia ⁠and reminds those fueling Putin’s war in Ukraine that ‌we will not let them hide,” Starmer ​said in a post ​on X.

The oil tanker was operating as part of Russia's shadow fleet. Photograph: Finnbarr Webster/Getty ImagesThe oil tanker was operating as part of Russia’s shadow fleet. Photograph: Finnbarr Webster/Getty Images

Starmer, who is facing a potential leadership challenge and lost his defence secretary last week over a dispute about military spending, had in March given permission for the British military to board and detain Russian ships that western governments say help Moscow export oil despite sanctions.

The prime ‌minister’s change of ⁠stance did not immediately have any impact on the number of Russian vessels under sanctions passing through UK waters, according to a ‌Reuters analysis which showed a similar number transited its waters before and after the announcement.

Until ​Sunday, Britain’s involvement in efforts to stop the vessels ​had been limited to supporting French and US operations. – Reuters