NATO allies Britain, Norway and the United States foiled a Russian military exercise near the Arctic Archipelago of Svalbard this spring. Russian vessels were training to deploy a secret weapon designed to disable critical undersea cables without leaving clear evidence.

Two Western officials told Reuters that the operation involved Russia’s Main Directorate of Deep-Sea Research, known as GUGI. The secretive undersea warfare unit used deep-sea submersibles to simulate the deployment of the disruptive technology.

British, Norwegian and US forces tracked the Russian vessels and confronted them at sea. The operation prevented the vessels from completing the exercise. They later left the area. Russia did not damage any cables during the operation.

Britain and Norway revealed in April that they had detected a covert Russian operation in Arctic waters. However, the discovery of the new technology, the location of the operation and the US involvement had not been reported earlier. The officials did not disclose how the technology works.

The incident comes amid growing Western concerns over Russian sabotage activities in Europe. Three US officials said some American intelligence analysts increasingly fear Russia could test NATO’s Article 5 mutual defence commitment. Western officials said attacks on subsea cables could form part of such an effort.

Undersea cables are vital for global internet connectivity and financial transactions. Some are no thicker than a garden hose. They run along the seabed or just below it. Their strategic importance has also made them targets during past conflicts, including the First and Second World Wars.

Two 1,400-km fibre-optic cables connect Svalbard with mainland Norway. They lie as deep as 2,700 metres underwater and carry large volumes of satellite data from SvalSat, the world’s largest satellite ground station and part of NASA’s Near Space Network.

Norway’s Defence Minister Tore Sandvik said, "Through our joint operation, we sent a clear message to Russia that they cannot operate covertly. We have made it unequivocally clear to Russian authorities that any attempt to target our critical infrastructure will be detected and met with consequences," he said. "It is in no one's interest to escalate tensions in the High North."

Britain’s Defence Ministry referred to its April 9 statements on Russian covert activities in and around Norwegian and British waters. Washington and London have imposed sanctions on GUGI. Russia’s Defence Ministry did not respond to Reuters’ request for comment. The Kremlin has repeatedly denied conducting sabotage operations in NATO countries.

Western officials said British and Norwegian officials also travelled to Moscow to present their findings on the new technology. They hoped the disclosure would discourage Russia from using it.

NATO allies have increased efforts to protect subsea infrastructure since the 2022 destruction of three of four Nord Stream pipelines. German prosecutors have indicted a Ukrainian man over the attack. Ukraine denies involvement.

Since 2023, more vessels have moved slowly over or near sensitive subsea infrastructure to map its location. Windward said drifting activity in the North Sea rose 52% last year to 13,079 vessels. In the South China Sea region, it increased 88% to 18,401 vessels.

Windward CEO Ami Daniel said, "The current thinking is that Russia and China are probably the most active and critical underwater threats," while Brookings Institution fellow Bruce Jones said Europe had expanded its dependence on seabed infrastructure while reducing its ability to protect it.