There are growing concerns that Russia is behind the severing of a crucial underwater Internet cable between Finland and Germany.

The 745-mile C-Lion1 cable malfunctioned just before 2am on Monday, manufacturer Cinia has said.

German Defense Minister Boris Pistorius told Brussels reporters on Tuesday that “nobody believes” that the cables in the Baltic Sea were “accidentally cut.”

“We have to conclude, without knowing exactly who did it, that it is a hybrid action and we also have to assume — without knowing it — that it is sabotage,” he added.

In a joint statement Finland and Germany said they were “deeply concerned about the severed undersea cable” and were investigating “an incident [that] immediately raises suspicions of intentional damage”.

Without explicitly naming Russia, the statement referenced “hybrid warfare by malicious actors” and added: “Safeguarding our shared critical infrastructure is vital to our security and the resilience of our societies”.

Cinia chief executive Ari-Jussi Knaapila told a press conference that the damage could require 15 days to repair.

“At the moment, there is no way to assess the cause of the cable break, but such breaks without external impact do not happen in these waters,” Mr Knaapila said.

The 730-mile-long cable follows a similar route to the Nord Stream gas pipelines between Germany and Russia, which blew up in September 2022 in an alleged act of sabotage.

Another telecomms cable in the Baltic Sea linking Lithuania and Sweden’s Gotland island was damaged on Sunday morning, according Lithuanian telecoms company Telia Lietuva.

The 135-mile internet link went down at about 8am on Sunday, the firm claims.