Sir Richard did not confirm if the drones were from Russia, but added it was “plausible” they had been ordered by Moscow.
Alongside Nato allies, he added that the UK would help Belgium “by providing our kit and capability” which he said was already being deployed.
It comes after Sir Richard warned in of an “increasingly certain world” in a Sunday Telegraph opinion column to mark Remembrance Sunday.
Citing Russia’s invasion of Ukraine, he said: “This conflict reminds us that peace is never guaranteed. It [the UK] must be defended, and sometimes at great cost”.
About 3,000 Brussels Airlines passengers were affected by the disruption, and the carrier said it faced “considerable costs” from cancelling or diverting dozens of flights.
German Defence Minister Boris Pistorius and the Belgian security services have said they suspect Russia, but Belgian Defence Minister Theo Francken has previously admitted there is no accompanying evidence.
“At first, drones flying over our military bases were seen as our problem,” Francken said earlier this week.
“Now it has become a serious threat affecting civilian infrastructure across multiple European countries.”
