The Finnish and German governments on Monday said an investigation was under way of a severed fibre optic communications cable running on the Baltic seabed and linking the two countries, and they cited concerns about the security of critical infrastructure.
The 1,200 km (745 miles) fibre optic cable running through the Baltic Sea from Helsinki, Finland's capital, to the German port of Rostock may have been severed by an outside force, Finnish state-controlled cyber security and telecoms network company Cinia said.
The C-Lion1 cable malfunctioned just after 0200 GMT, the company said.
The Finnish and German foreign ministries said in a joint statement that they were "deeply concerned" by the severed cable and that a thorough investigation was underway.
"Our European security is not only under threat from Russia's war of aggression against Ukraine, but also from hybrid warfare by malicious actors," they said. "Safeguarding our shared critical infrastructure is vital to our security and the resilience of our societies."
The sudden outage implied that the cable was completely severed by an outside force, although a physical inspection has not yet been conducted, Cinia's chief executive, Ari-Jussi Knaapila, told a press conference.
The damage occurred near the southern tip of Sweden's Oland island and could typically take between five and 15 days to repair, he added.
Cinia said it was working with authorities to investigate the incident.
Swedish public service broadcaster SVT reported that Swedish authorities were also investigating damage to a communications cable running between Lithuania and Sweden, close to the one that was severed.
"It is absolutely central that it is clarified why we currently have two cables in the Baltic Sea that are not working," Carl-Oskar Bohlin, minister of civil defence, told SVT.
The Swedish government did not immediately reply to Reuters' request for comment.
Last year a subsea gas pipeline and several telecoms cables running along the bottom of the Baltic Sea were severely damaged in an incident raising alarm bells in the region.
Finnish police investigating the 2023 case have named a Chinese container ship believed to have dragged its anchor as a prime suspect, but have not said whether the damage was believed to be accidental or intentional.
In 2022 the Nord Stream gas pipelines linking Russia to Germany in the Baltic Sea were destroyed by explosions in a case that remains under investigation by German authorities.
