An IISS report says it is “highly likely” the Kremlin used Russia-linked “shadow fleet” vessels to support drone operations over Europe, including attempts to surveil military and nuclear-related installations and probe how NATO air defenses respond to unmanned threats. The report tracked 144 suspected drone sightings across multiple European countries—such as Germany, France, Belgium, the Netherlands, the UK and Denmark—where incidents prompted repeated disruptions to civilian aviation and raised concerns about security near sensitive sites.

The IISS assessment argues that using ships at sea helps Russia maintain deniability, since drones can be launched closer to targets without clearly signaling origin points. The report links the sightings to the presence of sanctioned “shadow fleet” ships in relevant areas and notes that drones were sometimes detected without triggering traditional radar responses.

The findings come amid broader European efforts to address drone risks, with NATO countries also cautioning that attribution remains difficult when evidence does not definitively connect individual drones to specific launch platforms.