Germany’s defence minister said officials had to assume damage to two data cables under the Baltic Sea, one of which ends in Germany, was caused by sabotage — although he said they had no proof at present.

Damage was detected on Monday to the C-Lion1 cable that runs nearly 750 miles (1,200km) from the Finnish capital, Helsinki, to theGerman port city of Rostock. Another cable between Lithuania and Sweden was also damaged.

Speaking in Brussels, German defence minister Boris Pistorius said that Russia posed not just a military but also a hybrid threat, and that Europe needed to take a broad approach to defence. He said the damage to the two cables was “a very clear sign that something is afoot”.

“No-one believes these cables were severed by mistake, and I also don’t want to believe versions that it was anchors that by chance caused damage to these cables,” he said at a regular meeting of European Union defence ministers.

“So we have to state — without knowing in concrete terms who it came from — that this is a hybrid action. And we also have to assume — without already knowing it, obviously — that this is sabotage.”

The foreign ministries of Finland and Germany had already said on Monday evening that the damage raised suspicion of sabotage.

They said in a joint statement that the damage came at a time when “our European security is not only under threat from Russia’s war of aggression against Ukraine, but also from hybrid warfare by malicious actors”.

The statement said the countries were investigating the incident, and that it was crucial that such “critical infrastructure” be safeguarded.