UK navy tracked three Russian submarines near undersea cables, damage would 'have serious consequences,' Putin warned — US and allies expand seabed protection efforts

A Royal Navy warship and P8 maritime patrol aircraft have tracked three Russian submarines, including two GUGI-class deep-sea vessels, attempting to survey undersea cables and pipelines in the North Atlantic during a month-long operation, UK Defence Secretary John Healey told a Downing Street press conference on Thursday morning.

Healey said the Russian activity took place while international attention was focused on the U.S.-Israel war in Iran, and that the Russian subs abandoned the mission without damaging any infrastructure.

Healey declined to specify the exact location or the cables involved, saying only that the activity didn’t take place in UK territorial waters. He said UK forces would work with allies to verify that no pipelines or cables had been damaged. Addressing Vladimir Putin directly, Healey said any attempt to damage undersea cables or pipelines would "have serious consequences.”

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The GUGI-class is a Russian special-mission submarine programme associated with seabed operations and reconnaissance, and the presence of two such vessels alongside a third submarine clearly points to surveillance efforts. Healey said the operation demonstrated that UK armed forces were capable of detecting, deterring, and responding to threats against vital undersea infrastructure.

Undersea cables carry the majority of international data traffic, and the global network of them is expanding rapidly to meet AI-driven capacity demand. As of mid-February, 119 new cables were planned globally, up from 98 in January 2025 and 66 in January 2020, according to TeleGeography chief research officer Tim Stronge, cited by the Wall Street Journal.

Unfortunately, the cables themselves are difficult to harden. A typical armored submarine cable is roughly 1.4 inches in diameter, wrapped in galvanized steel wires around a copper sheath and optical fibers. Anchor drags from large commercial vessels remain the primary threat to them, and additional steel plating can’t reliably prevent a snagged cable from being ripped up. Close to shore, cables are buried, but only to limited depths.

Several nations are exploring military solutions to ward off attacks on cable infrastructure, with NATO having launched an effort known as Baltic Sentry in January. It uses ships, drones, and aircraft to patrol the Baltic Sea, and was launched after a Russia-linked vessel cut cables in 2024.

NATO Allied Maritime Command spokesperson Commander Arlo Abrahamson told the Wall Street Journal that there were no suspected malign incidents for roughly a year after patrols began, until Finnish authorities detained a vessel late last year on suspicion of cable damage. It’s understood that there are plans to deploy more uncrewed surface vessels during this year's operation.

It’s not just Europe that’s facing undersea cable sabotage. Taiwan has had to increase its coast guard patrols and legal penalties after a series of cable cuts in 2023 and 2025. Last year, a Taiwan court sentenced the Chinese captain of a Togo-flagged ship to three years in prison for intentionally damaging a cable.

In response, private operators are rerouting around contested waters, with the planned I-AM Cable and Candle systems both avoiding the central South China Sea. New monitoring technology is also being deployed, including distributed acoustic sensing, which uses laser pulses down the length of a cable to detect nearby vessels, and Anduril Industries' Seabed Sentry, a sonar-equipped device designed to sit on the ocean floor for months at a time.

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