Sabotage Against Undersea Infrastructure in the Baltic Sea and Suspicion of Russia

After the start of the Ukraine–Russia war, threats against Europe’s energy and communication security gain a new dimension. The Baltic Sea in particular turns into a “shadow war” zone with mysterious sabotage incidents against undersea infrastructure that are assessed to be carried out by Russia.

These activities are mostly carried out through civilian merchant ships, called the “ghost fleet.” With these methods, Russia is thought to punish Western countries that support Ukraine militarily and politically, and to seek strategic advantage in a possible conflict.

Undersea and Seabed Infrastructure

Although most activities at sea are carried out on the surface, operations undersea and on the seabed hold great importance. These activities are mostly commercial and economic but are also widely conducted for military or scientific purposes.

Subsea pipelines and power transmission lines are key underwater infrastructures used for global energy transfer. Subsea pipelines provide a significant portion of worldwide energy transmission.

However, repeated damages and disruptions in the Baltic Sea over the past two years reveal the vulnerability of these vital infrastructures. Western intelligence reports and regional investigations indicate that Russia has a direct or indirect role in these incidents. Strong suspicions exist that Russian ships disguised as civilian merchant vessels, called the “ghost fleet,” are used in seabed sabotage operations.

Fragility of Undersea Infrastructure and Russia’s Strategy

Kremlin’s strategy is assessed as creating pressure on European countries supporting Ukraine through covert operations, targeting energy and communication security. In this way, Russia aims to create deterrence during peacetime and to cut communication among allied countries in case of a NATO–Russia conflict, gaining strategic advantage.

The Baltic Sea has an average shallow depth of 55 meters, which makes infrastructures vulnerable to both technical failures and sabotage. Pipelines and communication cables lie unprotected on the seabed; accessing them does not require advanced technology. For this reason, the line between “accidents” and “deliberate sabotage” becomes increasingly blurred.

Baltic countries and European allies launch investigations against Russia following the incidents. Sweden, Finland, and Estonia cooperate in joint work, while NATO and the EU increase surveillance activities in the region. However, the lack of direct evidence pointing to Russia creates diplomatic uncertainty.

Meanwhile, Russia’s investments in seabed operation capabilities draw attention. Russia develops both manned mini-submarines and unmanned underwater vehicles, strengthening its ability to operate in deep seas and continental shelves. These capabilities raise concerns that Western energy and communication lines may be targeted in the future.

Undersea Infrastructure Incidents in the Baltic Sea

EE-S1 Communication Cable – October 7, 2023 (Estonia–Sweden)
The EE-S1 fiber optic cable connecting Estonia and Sweden suffers disruption on October 7, 2023. The activity of merchant ships in the area raises suspicion. It is suspected that the damage is caused by an anchor rather than an accident. This event shows the vulnerability of critical infrastructure and becomes the first link in a chain of incidents.

Balticconnector Pipeline – October 8, 2023 (Finland–Estonia)
Only one day later, the Balticconnector natural gas pipeline between Finland and Estonia suffers damage. Although no explosion marks are found, the pipeline is determined to be damaged by external physical interference. Finland declares there is strong evidence of sabotage and launches an investigation. This incident increases the threat to regional energy and communication security.

BCS East-West Interlink Cable – November 18, 2024 (Lithuania–Sweden)
The BCS East-West Interlink telecommunications cable between Lithuania and Sweden is cut on November 18, 2024. Authorities state the damage is caused by external interference. The Swedish Navy investigates merchant ships in the region. The nature of the damage weakens the possibility of an accident. The incident shows similarities to the Balticconnector sabotage, focusing suspicion on Russia.

C-Lion1 Communication Cable – November 18, 2024 (Finland–Germany)
On the same day as the BCS East-West Interlink cable damage, the C-Lion1 communication cable between Finland and Germany also suffers disruption. The simultaneity strengthens the suspicion of coordinated sabotage and raises tension further. Operators determine that the cable is physically pulled from outside.

C-Lion1 Communication Cable – December 25, 2024 (Finland–Germany)
The C-Lion1 cable is cut again on December 25, 2024, shortly after the first incident. Finland declares that evidence of deliberate sabotage exists. The repetition highlights the difficulty of repair efforts and shows that attacks can be repeated.

Estlink 2 Power Cable – December 25, 2024 (Estonia–Finland)
The Estlink 2 power cable, which provides the electricity connection between Estonia and Finland, was disabled on the same date as the renewed damage to the C-Lion1 communication cable. The outage caused short-term disruptions in the energy supply security of both countries.

FAC-1, FAC-2 Communication Cables – December 25, 2024 (Estonia–Finland)
Simultaneously with the Estlink 2 incident, four fiber optic communication cables owned by a Finnish telecommunications operator are damaged. Multiple critical infrastructures being hit on the same day strengthens the suspicion of a hybrid attack.

Latvia–Gotland Fiber Optic Cable – January 2025 (Latvia–Sweden)
In January 2025, a fiber optic cable between Latvia and Sweden’s Gotland Island suffers damage. Swedish authorities detain a Malta-flagged ship as a suspect, but no direct sabotage evidence is found. The incident is seen as part of a repeating pattern and shows that sabotage in the Baltic Sea becomes a permanent security problem for regional countries.

Joint Seabed Security Initiative by Six European Countries

This joint initiative emphasizes that sabotage risks in the Baltic Sea are not only a problem for Baltic countries. The incidents in the Baltic Sea highlight a new security vulnerability that affects the whole world. Energy pipelines, fiber optic cables, and power connections are critical not only for Europe but also for the economic and military stability of states from Asia to America. Therefore, sabotage against undersea infrastructure increasingly becomes a global security problem.

Recent attacks and suspicious disruptions show that the nature of war is changing. Alongside conventional military operations, a new domain called “seabed warfare,” targeting undersea infrastructure, comes to the forefront. These attacks are used as part of hybrid warfare doctrine, targeting the economic lifelines and communication networks of the adversary instead of its armed forces. Disrupting pipelines and cables affects not only the economy of a country but also its security mechanisms directly.

Seabed warfare is assessed to be used more frequently in the future. Therefore, countries must not only protect existing infrastructures but also develop new military units, special task forces, and tactics.