A Royal Navy attack submarine surfaced close to a Russian spy ship off the UK coast in an extraordinary warning to stop spying on British undersea cables, the defence secretary has revealed.

John Healey, in a highly unusual statement to MPs, said the incident involving HMS Astute happened in November but the research vessel, called Yantar, then returned to UK waters this week.

To counter the first spying mission, which passed through Cornish waters, he said he changed the navy's rules of engagement to enable British warships and the submarine to get closer to the vessel and better track its activities.

In a message to Russian President Vladimir Putin, Mr Healey said: "We see you. We know what you are doing. And we will not shy away from robust action to protect this country."

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It is very rare for the UK to reveal details about the movement of its top secret fleet of nuclear-powered submarines.

A decision to tell parliament that one of the submarines had surfaced next to the surveillance vessel underlines the extreme seriousness that the UK views the Russian activity back in November and again this week.

Mr Healey said the Russian ship had been used for gathering intelligence and mapping the UK's critical underwater infrastructure.

The UK and its NATO allies are increasingly concerned about the risk that President Putin's country poses to offshore cables, pipelines and other infrastructure.

It is part of what British and American spy chiefs have described as a "reckless campaign of sabotage" across Europe by Russian intelligence officers.

A senior NATO official even warned in a recent interview with Sky News that there was a "real prospect" an unconventional attack by Russia against NATO - such as an act of sabotage or arson - will cause "substantial" casualties.

Describing the most recent sighting, the defence secretary said Yantar entered the "UK exclusive economic zone about 45 miles off the British coast" on Monday.

The spy ship is understood to have been in the English Channel, heading east to the North Sea

Mr Healey said that for the last two days, the Royal Navy has deployed Type 23 frigate HMS Somerset and patrol ship HMS Tyne to "monitor the vessel every minute through our waters".

A P-8 Poseidon maritime patrol aircraft was also deployed to track the vessel from the sky.

The defence secretary said the ship "has complied with international rules of navigation" and has since sailed into the North Sea.

Russia has said Yantar is an oceanographic research ship which is operated by its defence ministry.

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Second incident in months

Mr Healey told the House of Commons it was the second time Yantar had entered British waters in recent months, after it was detected in November "loitering over critical undersea infrastructure".

Back then, the Royal Navy nuclear-powered submarine was used to warn off the spy ship.

The defence secretary also said he changed the navy's rules of engagement so "our warships can get closer and better track the Yantar".

'Monitoring its every move'

RAF maritime patrol aircraft, minehunter HMS Cattistock, offshore patrol vessel HMS Tyne and surveillance ship RFA Proteus were also deployed "to shadow Yantar's every movement".

Mr Healey said: "I authorised a Royal Navy submarine, strictly as a deterrent measure, to surface close to Yantar to make clear that we had been covertly monitoring its every move.

"The ship then left UK waters without further loitering and sailed down to the Mediterranean."

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Mr Healey warned: "Russia remains the most pressing and immediate threat to Britain, and I want to assure the House and the British people that any threat will be met with strength and resolve."

P-8 Poseidon and Rivet Joint spy planes will join the NATO operation to protect undersea cabling in the Baltic Sea, while RFA Proteus has also been deployed to monitor offshore infrastructure.

(c) Sky News 2025: Royal Navy attack submarine warned off Russian spy ship from UK waters