Norway’s police security service (PST) has accused Russia of being behind a cyberattack in April that took control of a dam in Bremanger, western Norway, and forced open a floodgate for about four hours, according to Reuters.

PST chief Beate Gangås said on August 14 that the incident was part of a growing pattern of hostile cyber activity from pro-Russian groups.

The attack occurred on April 7 at the Bremanger dam near Svelgen, releasing about 500 litres of water per second until operators stopped it. Water levels were well below flood capacity, so no injuries or damage were reported. The dam is used mainly for fish farming rather than national power generation.

Norway’s organized crime police unit, Kripos, said a video of the incident appeared on Telegram the same day, watermarked with the name of a pro-Russian cybercriminal group. This group is believed to unite several actors involved in previous cyberattacks against Western targets.

The Russian embassy in Oslo rejected PST’s claims as “unfounded and politically motivated” Reuters said.