ShareSaveAdd as preferred on GoogleOlivia IrelandMinistry of DefenceThree Russian submarines conducted a "covert" operation of cables and pipelines in waters north of the UK, Defence Secretary John Healey said.
A British warship and aircraft were deployed to deter the "malign" activity by Moscow and there was "no evidence" of any damage to UK infrastructure in the Atlantic, he added.
Addressing Russian President Vladimir Putin directly, Healey said: "We see you. We see your activity over our cables and our pipelines, and you should know that any attempt to damage them will not be tolerated and will have serious consequences".
The UK is dependent on its undersea cables and pipelines for its data and energy.
There are around 60 undersea cables which come ashore at several parts along the UK coastline, particularly around East Anglia and South West England.
More than 90% of the UK's day-to-day internet traffic travels via these undersea cables.
Healey told a Downing Street press conference on Thursday that Russia had sent an Akula class submarine as a diversionary tactic while two of its Guggi spy submarines carried out the surveillance of these cables.
Healey said when the first Akula submarine was monitored it soon left UK waters and went back to Russia, while the two Gugi vessels remained.
The Royal Navy deployed a Type 23 frigate HMS St Albans, RFA Tidespring and Merlin helicopters to track all three of the Russian submarines.
Other nations were involved in tracking the Russian activity - though Healey only mentioned Norway by name.
"Our armed forces left [Russia] in no doubt that they were being monitored, that their movements were not covert, as President Putin planned, and that their attempted secret operation had been exposed," Healey said.
"We watched them, we were able to track them, we dropped sonar buoys to demonstrate to them that we were monitoring every hour of their operation."
Healey also claimed that Putin had sought to capitalise on the world being "distracted" by war in the Middle East and that it was Russia that posed the "primary threat to UK security".
He said Moscow still "poses a threat" but expressed confidence the UK could track and monitor future activity while continuing to expose "any covert operations that Putin wants to mount that may threaten our vital interests".
Underwater cables and pipelines are a major piece of critical infrastructure worldwide.
More than 600 undersea cables connect the world by 870,000 miles (1.4m km) carrying electricity and information across oceans and seas, coming ashore often at discreet locations.
The UK also relies on a network of underwater gas pipelines, primarily in the North Sea, which provides essential energy from the UK and Norwegian Continental Shelves.
This includes the 724 mile-long (1,166km) Langeled pipeline between Norway and the UK.
About 77% of the UK's gas imports come from Norway through pipelines lying under the North Sea.
BBC InDepth revealed in 2025 that Russia was waging "hybrid warfare" against the UK and western Europe, with the aim of punishing or deterring Western nations from continuing their military support of Ukraine.
"Hybrid warfare" is when a hostile state carries out an anonymous, deniable attack, usually in highly suspicious circumstances, but stops short of being an attributable act of war.
The Russian embassy has previously said it was "not interested in British underwater communications."
