A submarine cable was damaged in the Baltic Sea, the fourth case reported by the Nordic countries in the past two months. View on euronews

An undersea fiber optic cable between Latvia and Sweden was damaged on Sunday, likely as a result of external influence, Latvia said, triggering an investigation by local and NATO maritime forces in the Baltic Sea.

Swedish authorities boarded a vessel suspected of being involved in an earlier underwater sabotage of cables in the Baltic Sea on Monday.

The Arelion submarine cable, which connects the Swedish island of Gotland to Lithuania, and the C-Lion 1 submarine communications cable that runs between Finland's capital Helsinki and the German city of Rostock were also damaged in mid-November near Sweden's territorial waters.

Sweden detained a vessel suspected of damaging a subsea data cable connecting it with Latvia, the third such incident in the Baltic Sea in the past three months.

Latvia said it had dispatched a warship on Sunday after damage to a fibre optic cable to Sweden that may have been "due to external factors". The statement added: "Based on current findings, it is presumed that the cable is significantly damaged due to external factors.

A subsea data cable between Latvia and Sweden was damaged early Sunday, sparking a criminal investigation, a third such incident in the Baltic Sea in the past three months.

After a fiber optic cable was damaged near Sweden, Latvia sent a patrol boat to inspect a suspicious vessel in the Baltic Sea. Sweden later said it seized a vessel believed to have carried out the sabotage.

As tensions rise, NATO has launched Baltic Sentry 2025 to enhance security and resilience. European Commission President Ursula von der Leyen has emphasized the need for greater coordination in protecting critical infrastructure from sabotage.

Norway, which is NATO's monitor for a vast 2 million sq km area of the North Atlantic used by the Russian Northern Fleet's nuclear submarines, says it will invest in long-range surveillance drones for a planned Arctic base.

Several undersea cables running under the surface of the Baltic Sea have been damaged in suspected sabotage incidents in recent months.