Sweden's Security Service has taken over an investigation regarding unauthorized drones at three Swedish nuclear power plants on Friday, it said in a statement on Monday.
Police in Sweden deployed patrols and helicopters to the Forsmark nuclear plant to hunt for a drone seen flying over the site late on Friday, but were unable to catch the unmanned vehicle.
Police said the drone was large and able to operate despite high winds at the Forsmark plant.
The Security Service said on Monday drones had also been sighted at Sweden's two other nuclear power plants, in Oskarshamn and Ringhals. Around 30% of Sweden's total power production comes from the three plants.
The incidents came a day after Sweden's military started patrolling the main town on the Baltic Sea island of Gotland amid increased tensions between NATO and Russia and a recent deployment of Russian landing craft in the Baltic.
"In general, the security threats against Sweden have increased with a broader and more in-depth intelligence threat and a more complex threat picture," the Security Service said in the statement.
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