The Belgian government has told the BBC it is urgently trying to acquire drone defences after a sighting forced its main airport near Brussels to close temporarily.

Flights were paused at Zaventem airport on Thursday night, after drones were spotted nearby. They were also seen in other locations, including a military base.

"At first, drones flying over our military bases were seen as our problem," Defence Minister Theo Francken said. "Now it has become a serious threat affecting civilian infrastructure across multiple European countries."

Francken said several European allies have offered assistance, and he had accepted help from the German military which is providing anti-drone defences.

About 3,000 passengers of Brussels Airlines were affected by the disruptions, and the carrier said it faced "considerable costs" from cancelling or diverting dozens of flights.

"EU compensation schemes don't apply here," Joelle Neeb of Brussels Airlines told the BBC.

"But we do have an obligation to make sure passengers get to their final destination as soon as possible by offering refunds of alternative flights, as well as covering their hotels and transport."

She added that drones were a "new threat" and as such, the airline was adapting its contingency plans.

"When our main airport is closed even for just 30 minutes, that has a big impact and we need to act fast."

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.