Three Russian submarines conducted a "covert" operation over 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 points 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 GUGI spy submarines carried out the surveillance of these cables.

Healey said the Akula submarine soon left UK waters and went back to Russia after it was monitored, 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 mentioned only 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 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".

Prime Minister Sir Keir Starmer said he was "determined to protect the British people from paying the price for Putin's aggression in their household bills", adding this was why the UK would not "shy away from taking action and exposing Russia's destabilising activity that seeks to test our resolve".

Referring to reports this week that Russian oil tankers were escorted through the English channel by the Russian navy, Reform UK leader Nigel Farage said: "If we have learnt one thing in the last month, it is that we do not have an operational Royal Navy at any level in this country and that for us needs to be a massive wake-up call."

A former UK defence attaché in Moscow told the BBC "the rhetoric is a bit tired by now."

John Foreman, a retired Royal Navy officer, said: "We're well aware of the Russian threat. The question is whether we're doing something about it."

He went on to say the UK is "hard-pressed" to maintain its security, pointing out the decommissioning of two tankers, RFA Wave Knight and RFA Wave Ruler.

"I don't know how we are going to dig ourselves out of this nadir of maritime security that we have found ourselves in," Foreman said.

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.

Dr Sidharth Kaushal, a sea power researcher at the Royal United Services Institute (RUSI), told BBC Verify the Russian military's GUGI unit operates deep-diving mini-submarines supported by a larger "mothership".

These vessels are "complex targets", Kaushal said, because they are designed to avoid detection by reducing the amount of noise they emit, how much water they displace and how detectable they are to magnetic sensors.

Kaushal added it is likely the submarines were still able to gather data on the UK's undersea cable network despite being monitored by the Royal Navy.

He said the UK's ability to constrain their operations during peacetime is "limited" and notes that militaries and private organisations can legally carry out such monitoring "as long as they are in international waters".

But Kaushal said the Royal Navy may have gathered vital intelligence by monitoring the operation, in order to learn more about what is being mapped, the tactics used by Russia, and "potentially recover any surveillance assets left behind".

The UK also relies on a network of underwater gas pipelines, primarily in the North Sea, which provide essential energy from the UK and Norwegian Continental Shelves.

These include 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".