The latest incident came as nations around the Baltic Sea scrambled to bolster their defences after the suspected sabotage of undersea cables in recent months, with some observers blaming Russia.

Latvia's navy said it had identified a "suspect vessel", the Michalis San, which was near the location of the incident along with two other ships.

Several websites tracking naval traffic said the Michalis San was headed for Russia.

"We have a warship patrolling the Baltic Sea around the clock every day and night, allowing us to quickly dispatch it once we learnt about the damage," Latvian navy commander Maris Polencs said at a briefing Sunday.

Prime Minister Evika Silina said: "We have notified the Swedish authorities and are working together with them to assess the damage and its reason."

Swedish Prime Minister Ulf Kristersson said he had been in contact with Silina during the day.

"There is information suggesting that at least one data cable between Sweden and Latvia has been damaged in the Baltic Sea. The cable is owned by a Latvian entity," he posted on X.

"Sweden, Latvia and NATO are closely cooperating on the matter. Sweden will contribute with relevant capabilities to the effort to investigate the suspected incident," he added.

- Data 'disruption' -

Experts and politicians have accused Russia of orchestrating a hybrid war against the West as the two sides square off over Ukraine.

"The damage to the Sweden-Latvia undersea data cable is the latest in a series of systemic incidents affecting EU critical infrastructure," Ukraine's Foreign Minister Andriy Sybiga said Sunday on X.

"We express solidarity with the affected EU partners. An increased NATO presence in the Baltic Sea is critical to countering such threats."

NATO earlier this month announced it was launching a new monitoring mission in the Baltic Sea involving patrol ships and aircraft to deter any attempts to target undersea infrastructure in the region.

The damage occurred in Swedish territorial waters at a depth of at least 50 metres (55 yards), officials said.

The cable belongs to Latvia's state radio and television centre (LVRTC) which said in a statement that there had been "disruptions in data transmission services".

The company said alternatives had been found and end users would mostly not be affected although "there may be delays in data transmission speeds".

The statement added: "Based on current findings, it is presumed that the cable is significantly damaged due to external factors. LVRTC has initiated criminal procedural actions."

European Union President Ursula von der Leyen expressed her "full solidarity" with the countries affected by the incident.

"The resilience and security of our critical infrastructure is a top priority," von der Leyen wrote on X.

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