Finnish authorities detained a tanker suspected of belonging to Russia’s unofficial shipping network on Thursday after damage to critical undersea cables in the Baltic Sea.

The Eagle S, sailing under a Cook Islands flag, was intercepted during its journey from St. Petersburg to Egypt following damage to the Estlink 2 power cable linking Finland and Estonia, along with four data cables.

Finnish Customs head Sami Rakshit told reporters: “We assume at this stage that the vessel in question is a member of the shadow fleet” — a term Finnish authorities use to describe vessels suspected of helping Russia evade Western oil sanctions imposed after its invasion of Ukraine.

Nearly 70% of Russia’s oil is now transported by such vessels, according to an October analysis by the Kyiv School of Economics Institute, with ships often operating under foreign flags and selling to nations not bound by Western price caps.

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“This underlies the danger of the shadow fleet in the Baltic Sea,” Prime Minister Petteri Orpo said at a Helsinki press conference, while noting investigators had not yet established direct Russian involvement.

NATO Secretary General Mark Rutte discussed the “possible sabotage” with Estonian Prime Minister Kristen Michal, pledging alliance support. European Commission President Ursula von der Leyen commended Finland’s “swift action,” calling for enhanced protection of EU infrastructure.

While the power cable damage caused minimal disruption to Finland and Estonia’s energy exchange, communications services between Helsinki and the German city of Rostock were affected, according to Cinia, a digital communications company that owns one of the cables. Repairs could take several weeks.

Finnish authorities are investigating whether the vessel’s anchors caused the damage. The tanker remains anchored in Finnish waters as the probe continues in coordination with Estonian officials.

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