Drone sightings have caused major flight disruptions across Europe in recent months, including in Sweden, Norway and Denmark.
Some officials have blamed "hybrid warfare" by Russia, but the Kremlin has denied it has anything to do with it.
German Defence Minister Boris Pistorius also alleges Moscow's involvement, suggesting these latest sightings could be linked to European Union discussions to use frozen Russian assets to support Ukraine.
The controversial plan would see Kyiv receive a €140bn loan, but with the money being held in a Belgium-based bank, Euroclear. Brussels is nervous that it could be legally forced to pay Moscow back once the war in Ukraine ends.
Belgian security services also suspect Russia, but Francken admits there is currently no accompanying evidence.
In fact, amongst all the European finger pointing, there is no public proof suggesting Russia is responsible for these disruptions.
Suspicions are nevertheless being fuelled by more serious airspace incursions that Moscow has recently carried out in Eastern Europe, involving fighter jets and larger attack drones.
The Kremlin's likely goals are to both test European defences, as well as try to distract the bloc from supporting Ukraine, which is still on the receiving end of its invasion.
Additional reporting by Bruno Boelpaep.