Finnish authorities have seized a ship carrying Russian oil in the Baltic Sea because they suspect it caused the failure of a submarine cable between Finland and Estonia a day earlier and also damaged or disrupted four internet lines.

A crew from the Finnish Coast Guard boarded the Cook Islands-registered vessel, named Eagle S by authorities, on Thursday. The crew took command and steered the ship into Finnish waters, a coast guard official said at a news conference.

The director of the Finnish National Investigation Office, Robin Lardot, said: “From our side, we are investigating serious sabotage. It is our understanding that an anchor on the ship being examined is responsible for the damage.”

The Finnish Customs Service said it had seized the ship’s cargo and suspected the Eagle S was among Russia’s so-called shadow fleet of old tankers seeking to evade sanctions on the sale of Russian oil.

Two fiber optic cables from Finnish operator Elisa connecting Finland and Estonia were broken, while a third link between the two countries, owned by Chinese company Citic, was damaged, Finnish transport and communications agency Traficom said.

A fourth internet cable between Finland and Germany, owned by the Finnish group Cinia, was also cut, the agency said.

The Finnish and Estonian governments will hold extraordinary meetings on Thursday to assess the situation, they said in separate statements.

After a series of failures in power cables, telecommunications connections and gas pipelines since 2022, the Baltic Sea states are on high alert for possible acts of sabotage, although technical malfunctions and accidents also occur with underwater equipment.

Finnish power grid operator Fingrid said in a statement that repairing the 170km Estlink interconnector would take 2 months and that the outage increased the risk of winter power outages.

The Eagle S Panamax oil tanker crossed the Estlink 2 power cable at 1026 GMT on Wednesday, a Reuters review of MarineTraffic ship tracking data showed, identical to when Fingrid said the blackout occurred.

According to the data, the ship was stationary near the Finnish coast on Thursday afternoon, and a Finnish patrol ship stopped nearby.

United Arab Emirates-based Caravella LLCFZ, which owns the Eagle S, according to MarineTraffic data, did not immediately respond to a request for comment.

Peninsular Maritime, which MarineTraffic said is acting as technical manager for the ship, declined to comment outside of company hours.

Estonian Foreign Minister Margus Tsahkna said in a statement that damage to underwater facilities in the Baltic Sea had become so common that it was hard to believe it was merely the result of an accident or poor seamanship.

“We must understand that damage to submarine infrastructure has become more systematic and therefore must be viewed as attacks on our vital structures,” he said.

The outage of the 658 megawatt Estlink 2 began at midday local time on Wednesday, leaving only the 358 megawatt Estlink 1 operating between the two countries, Fingrid said.

Twelve Western countries said on December 16 that they had agreed on measures to “disrupt and deter” Russia’s shadow fleet to prevent sanctions violations and increase the costs to Moscow of the war in Ukraine.

On Thursday, Finnish President Alexander Stubb said on X: “We must be able to prevent the risks posed by ships in the Russian shadow fleet.”

Lithuanian Foreign Minister Kęstutis Budrys said the growing number of incidents in the Baltic Sea should serve as a clear and urgent warning to NATO and the EU to significantly improve protection of underwater infrastructure there.

Police in Sweden are conducting an investigation into the breakage of two Baltic Sea telecommunications cables last month, an incident that German Defense Minister Boris Pistorius suggested was caused by sabotage.

Finnish and Estonian police are also continuing to investigate damage caused last year to the Balticconnector gas pipeline connecting the two countries, as well as to several telecommunications cables, saying the damage was likely caused by a ship dragging at anchor.

The Russian-German Nord Stream gas pipelines, which run along the seabed in the same waters, were blown up in 2022 in a case that is still under investigation in Germany.