The gas pipeline started leaking at the weekend in Finland’s exclusive economic zone, and people familiar with the matter said on Tuesday the investigation is proceeding on the basis that it was sabotage. Finnish Prime Minister Petteri Orpo said the leak was caused by an “external source” as he declined to speculate on who may be responsible.

“It makes sense to increase our security of supply, secure critical infrastructure,” Orpo said. “The wise prepares. If something like this, so far inexplicable, happens, then it can also happen again.” 

European gas prices jumped, as the leak revived concerns about the vulnerability of undersea infrastructure particularly in the context of the war in Ukraine. 

Following the explosions on the Nord Stream pipelines from Russia to Germany last year — for which responsibility has yet to be determined — European countries have stepped up defence of their key assets.

Russia halted gas supply to Finland in May 2022, about a week after the Nordic country said it would apply for NATO membership in response to Russia’s invasion of Ukraine. The region now increasingly depends for gas on flows of LNG from the US.

The most vulnerable sites

Finland’s President Sauli Niinisto spoke to NATO Secretary General Jens Stoltenberg on Tuesday, and the group said it’s sharing information and “stands ready” to support its allies.

North Atlantic Treaty Organisation (NATO) members have increased monitoring of energy assets using satellites, aircraft, ships and submarines, with sites in the North Sea and Baltic Sea seen as among the most sensitive.

Read more: NATO Turns to Underwater Drones and AI in Bid to Deter Russia

The Balticconnector pipeline was put into use just over three years ago.

While the Baltic nations and Finland have reduced reliance on Russian gas even before cutting off imports from their eastern neighbour, they increasingly get liquefied natural gas from the US.

The interconnector linked the new LNG import terminal in Finland with Estonia, and similar floating terminals have been set up across Europe over the past year, including in Germany.