Fingrid, the operator of Finland’s national grid, said Estlink 2 remained out of service but that the damage “did not endanger the operation of the electricity system” in the country.
Repairs are expected to take “several months”.
“From our side we are investigating grave sabotage,” said Robin Lardot, director of Finland’s National Bureau of Investigation (NBI).
President Alexander Stubb posted on X that he had been given an “overview” of the cable breach from authorities.
He underlined the need to “avert the risks” posed by vessels that are part of the shadow fleet.
Finnish police have said the case is being investigated as “aggravated criminal mischief”.
The damaged cable had a transmission capacity of 650 megawatts and is 170km long (105 miles), 145km of which is submerged. The fault was located on Thursday in the submarine section.
The EU has threatened to impose further sanctions against Russia as a result of the incident and said it was “strengthening efforts to protect undersea cables”.
“We strongly condemn any deliberate destruction of Europe’s critical infrastructure,” the European Commission and the EU’s foreign policy chief, Kaja Kallas, said in a joint statement.
Estonia’s Foreign Minister Margus Tsahkna said on Thursday that damage to critical submarine infrastructure has become “so frequent” that it casts doubt on the idea this damage could be considered “accidental” or “merely poor seamanship”.
“We must understand that damage to submarine infrastructure has become more systematic and thus must be regarded as attacks against our vital structures,” Tsahkna said in a press release.
The foreign ministry added that Eagle S has been escorted to a Finnish port.
“In addition to circumventing sanctions, the shadow fleet is a security threat in the Baltic Sea and we cannot just sit and watch,” Tsahkna continued.
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A telecommunications cable running between Finland and Germany was severed in November, and an internet link between Lithuania and Sweden’s Gotland Island stopped working at around the same time.
German prosecutors are still investigating the explosion of Nord Stream gas pipelines between Russia and Germany in 2022.
And in October 2023 a natural gas pipeline between Finland and Estonia was severely damaged.
Finnish officials later said the incident had been caused by a Chinese container ship dragging its anchor.
