A flurry of drone sightings offshore Norway has raised concerns about the safety of the country’s critical oil and gas infrastructure, with authorities and operators scrambling to strengthen security for energy assets.

Measures in the works include creating no-fly zones offshore, giving “use-of-force” authority to private security providers on oil rigs, and high-tech solutions such as “geofencing” around oil and gas platforms.

The drone sightings come as gas exports to Europe are expected to rise over winter.

Drones occasionally have been spotted flying near energy infrastructure in recent years but sightings increased in late September, around the same time the Gazprom-controlled Nord Stream gas pipeline was ruptured, which has since been deemed an act of sabotage.