The Baltic Sea region is on high alert after a string of power cable, telecom link and gas pipeline outages since Russia invaded Ukraine in 2022. The NATO military alliance has boosted its presence with frigates, aircraft and naval drones.
Police have found that some incidents were caused by sabotage while others were accidental or remain subject to ongoing proceedings.
An undersea telecoms cable linking Sventoji in Lithuania to Liepaja in Latvia, two coastal towns some 65 kilometres apart, was damaged on January 2. Latvian police later boarded a ship docked at Liepaja and initiated criminal proceedings.
The police said on January 5 they found no evidence linking the ship to the damage of the cable, which belongs to Sweden's Arelion, and that they were investigating the incident further.
Finnish police on December 31 seized a cargo vessel en route from Russia to Israel on suspicion of sabotaging an undersea telecoms cable running from Helsinki across the Gulf of Finland to Estonia.
The vessel Fitburg was caught dragging its anchor in the sea and was subsequently directed into Finnish territorial waters, police said.
Investigators said the ship's 14 crew members were from Russia, Georgia, Kazakhstan and Azerbaijan. Two of them had been arrested while two others were banned from travel while an investigation was ongoing.
Sweden's Arelion said that one of its cables running from Finland to Estonia was also damaged on December 31, and that a cable from Estonia to Sweden stopped working on December 30.
An undersea fibre-optic cable connecting Latvia and the Swedish island of Gotland malfunctioned on January 26, prompting an investigation by NATO and police. Sweden later seized and boarded the Maltese-flagged bulk vessel Vezhen on suspicion that it had caused the damage in an act of gross sabotage.
Bulgarian shipping Company Navigation Maritime Bulgare said that Vezhen's anchor had dropped to the seabed in high winds and may have struck the cable, but denied any sabotage. A Swedish prosecutor later ruled the breach accidental and released the vessel.
The following month, Finnish telecoms operator Cinia said it had detected problems on its C-Lion1 link connecting Finland and Germany. It concluded that the damage might have occurred as early as January 26, the day of the Gotland incident.
The Estlink 2 undersea power cable connecting Finland and Estonia was damaged on December 25 along with four telecoms lines.
Finland launched a sabotage investigation and on December 26 seized a tanker carrying Russian oil on suspicion it caused the damage by dragging its anchor.
Finnish authorities said the Cook Islands-registered Eagle S was part of a "shadow fleet" used to circumvent sanctions on Russian oil exports. The European Union said it condemns any deliberate destruction of Europe's infrastructure.
The NATO military alliance said on December 27 it would boost its presence in the Baltic Sea region. The Kremlin said the same day that the ship's seizure was of little concern to it, and Russia has previously denied involvement in such incidents.
Finnish police said on December 29 they had found tracks on the seabed where they suspect the Eagle S of damaging the cables.
The owner of the Eagle S, United Arab Emirates-based Caravella, on December 30 filed a request with the Helsinki District Court seeking the release of the ship. This was rejected on January 3, 2025.
In October 2025, a Finnish court dismissed a case against the Eagle S captain and other crew members.
It ruled prosecutors failed to prove intent and that any negligence must be pursued by the ship's flag state or the crew's home countries. No charges were brought against the ship's owner, United Arab Emirates-based Caravella, and the vessel was released.
Two undersea fibre-optic communications cables located more than 100 nautical miles (about 200 kilometres) apart in the Baltic Sea were severed on November 17 and 18, raising suspicions of sabotage.
A 218-kilometre internet link between Lithuania and Sweden's Gotland island went out of service at about 08:00 GMT on November 17, according to Lithuania's Telia Lietuva, part of Swedish Telia Company.
A 1,200-kilometre cable connecting Helsinki to the German port of Rostock stopped working around 02:00 GMT on November 18, Finnish state-controlled cyber security and telecoms company Cinia said.
Investigators in the countries involved zeroed in on Chinese bulk carrier Yi Peng 3, which left the Russian port of Ust-Luga on Nov. 15, and a Reuters analysis of MarineTraffic data showed that the ship's coordinates corresponded to the time and place of the breaches.
China allowed representatives from Germany, Sweden, Finland and Denmark on December 21 to board the Yi Peng 3 along with Chinese investigators, after a month-long diplomatic standoff during which the ship sat still in a Danish shipping lane.
A Swedish inquiry found no conclusive evidence to suggest that the ship deliberately dragged its anchor to damage the cables, Sweden's Accident Investigation Authority said in April.
A subsea gas pipeline, the Balticconnector, which links Finland and Estonia under the Baltic Sea, was severed by what Finnish investigators determined was Chinese container vessel NewNew Polar Bear dragging its anchor in the early hours of October 8, 2023.
Estonian police suspect the ship of also damaging telecoms cables connecting Estonia to Finland and Sweden on October 7-8, before hitting the gas pipeline on its way to a port near St Petersburg in Russia.
The ship's captain appeared in court in Hong Kong in a pre-trial hearing last year accused of causing "criminal damage" to the pipeline and cables. This was according to a Hong Kong charge sheet seen by Reuters.
Nord Stream 1 and Nord Stream 2, built across the Baltic Sea by Russia's state-controlled Gazprom to pump natural gas to Germany, were damaged on September 26, 2022.
Swedish seismologists registered several subsea blasts, some 17 hours apart, off the Danish island of Bornholm, that ruptured three out of four pipelines in the Nord Stream system, releasing methane into the atmosphere.
In the investigations, Sweden found traces of explosives on several objects recovered from the site, confirming it was a deliberate act, but Sweden and Denmark closed their investigations without naming suspects in 2024.
No one has taken responsibility.
Some Western officials have suggested Moscow blew up its own pipelines, an interpretation dismissed by Russian President Vladimir Putin.
Russia has blamed the United States, Britain and Ukraine for the blasts, which largely cut Russian gas off from the European market. Those countries denied involvement.
In August 2024, Germany asked Poland to arrest a Ukrainian diving instructor accused of being part of a team that blew up the Nord Stream pipelines. Poland said the man left the country before he could be detained.
In November 2025, Italy's top court approved the handover to Germany of a Ukrainian man suspected of coordinating the sabotage. A Polish court last year ruled against handing over a Ukrainian diving instructor sought by German prosecutors.
(Reporting by Anne Kauranen in Helsinki, Nerijus Adomaitis in Oslo, Johan Ahlander in Gothenburg, Stine Jacobsen in Copenhagen, Andrius Sytas in Vilnius and Anna Ringstrom in Stockholm; Editing by Andrew Cawthorne and Timothy Heritage)