‘NATO Lake’ Sabotage Feared as Two Undersea Cables Damaged in 24 Hours

Two undersea cables in the Baltic Sea were disrupted in quick succession, NATO officials and local telecommunications companies have said. It raises fears of sabotage from “malicious actors” in the region at a time when the alliance is at odds with Russia.

Unseen but crucial, undersea cables prop up internet services and communications, as well as many other aspects of daily life often taken for granted. Around 99 percent of the world’s data runs through undersea cables, but they are vulnerable to attack, in what is known as hybrid warfare.

A cable linking Finland and Germany was “severed,” Helsinki and Berlin’s foreign ministers said in a joint statement on Monday, adding they were “deeply concerned.” Cinia, a Finnish state-controlled telecommunications company, said the cable was damaged close to the southern edge of the Swedish island of Öland, roughly 700 kilometers [435 miles] from Helsinki, at around 4 a.m. local time on Monday.

The cable, known as C-Lion1, stretches 1,173 kilometers [just under 730 miles] and links central Europe to Finland and other Nordic nations. It typically takes between five and 15 days to repair this type of cable, the company said, adding: “The details of the fault are yet not known and are currently being investigated.”

Telecommunications firm Telia Lithuania said separate remarks that an undersea internet cable linking Lithuania and Sweden was “cut” on Sunday morning at approximately 10 a.m. local time.

“The systems immediately reported that we had lost contact,” Andrius Šemeškevičius, technology manager for the company, told Lithuanian broadcaster LRT.

“Our European security is not only under threat from Russia’s war of aggression against Ukraine, but also from hybrid warfare by malicious actors,” the two ministers said.

The two damaged cables cross in a certain section of the Baltic Sea, Šemeškevičius said. “Since both were interrupted, it is obvious that there was no accidental dropping of one ship’s anchor; it could be something more serious.”

Mystery still surrounds the destruction of the Nord Stream pipelines linking Russia to Germany through the Baltic Sea in fall 2022, while an undersea cable linking Sweden to Estonia was damaged in October 2023. A gas pipeline linking Estonia to Finland was also damaged in the same month, later blamed on a Chinese ship dragging its anchor.

NATO has been ringing alarm bells in recent years over Russia’s skill with hybrid warfare. In May, it held a meeting dedicated to strategizing how to protect the alliance’s critical undersea infrastructure.

“Russia has spent a considerable amount of effort investing in capabilities that would allow it to pose a threat to European critical infrastructure,” the U.K.-based Royal United Services Institute (RUSI) defense think tank said last year.

German Defense Minister Boris Pistorius said on Tuesday that “no one believes that these cables were cut accidentally.”

“I also don’t want to believe in versions that these were anchors that accidentally caused damage over these cables,” he said, in remarks reported by Reuters. “Therefore we have to state, without knowing specifically who it came from, that it is a ‘hybrid’ action. And we also have to assume, without knowing it yet, that it is sabotage.”

The Baltic Sea has been referred to as a “NATO lake,” as it is bracketed almost entirely by alliance members since Finland and Sweden joined. Russia’s Kaliningrad exclave, home to its substantial Baltic Sea Fleet, is sandwiched between NATO members Poland and Lithuania.

An unnamed U.S. official told CNN in early September that they were worried Russia’s “decision calculus for damaging US and allied undersea critical infrastructure may be changing.”

Moscow is cultivating its naval fleet designed for undersea sabotage mainly through its secretive General Staff Main Directorate for Deep Sea Research, or GUGI, the official said.