Sweden's prosecution office said it launched a probe into "sabotage" over damage to two undersea Baltic Sea cables, connecting Lithuania and Sweden and Finland and Germany.
"The offense is currently being investigated as sabotage. The preliminary investigation is ongoing and at an early stage. There is no further information to share about the investigation at this time," prosecutor Henrik Soderman said in a statement just hours after neighboring Finland said it had also opened a police investigation.
The war in Ukraine and the destruction of the Nord Stream pipelines forced Germany to look elsewhere for energy and it has built a series of gas terminals on its coast.
Increased drone activity around the new infrastructure however raised suspicions that the terminals were being scouted "for the purposes of sabotage," German officials said.
According to German media reports, the reconnaissance was carried out by unmanned Russian military aircraft.
German Foreign Minister Annalena Baerbock said in October that Moscow was using "hybrid means" to target Germany, adding: "We see many, many examples, time and again."
Drones above industrial sites were "not there to observe the beautiful local landscape, but because there is a chemical park there and a... storage facility for nuclear waste nearby," she said.
Russian ships in the North and Baltic Seas have caused increasing concern for NATO countries in the region.
Belgium launched an investigation in early 2023 after a Russian spy ship off its North Sea coast was suspected of surveying key energy and communications links.
In July 2024, Finland said a Russian research vessel violated its territorial waters, shortly after it joined the NATO military alliance.
Russian vessels were systematically surveying critical infrastructure, including wind farms, pipelines, and cables in the North and Baltic Seas, according to a report by German broadcasters NDR, WDR and newspaper Sueddeutsche Zeitung.
"We consider the danger to be very real," German intelligence chief Bruno Kahl told media.
Moscow was "accelerating its own preparations to be able to act militarily against the West", Kahl said.
In April, Estonia and other Baltic states warned that widespread GPS jamming increased the threat of an aviation accident.
The disturbance to location services was blamed on Russian "hybrid activity" in the region, Estonia said.
The disruption led Finnish carrier Finnair to suspend flights to the Estonian city of Tartu, near the Russian border.
The airline's pilots have noticed an increase in interference since 2022, including the airspace close to Russia's Kaliningrad region on the Baltic Sea.
Russia has also created alarm by starting disputes over borders in the Baltic Sea.
Moscow published a resolution this year that showed it planned to unilaterally change its maritime frontiers with Finland and Lithuania from 2025.
Russian border guards in May removed buoys from the Narva River which showed the border with Estonia, officials in Tallinn said.
The disappearance of the markers was part of a "broader pattern" by Moscow to use "tools related to the border to create fear and anxiety", Estonian Prime Minister Kaja Kallas said.
