Some 400-500 passengers had to spend the night at Zaventem airport because of the sightings, Brussels Airport spokesman Ariane Goossens told AFP.

“The situation will return to normal during the day” as flights restart, she said.

Last night, air traffic was also halted as a precaution at the second-largest airport Charleroi, operators there said.

Skeyes, the company responsible for air traffic control in Belgium, halted flights twice last night, around 7pm to 10pm, after suspected drones were seen near the Brussels-Zaventem airport and that of Liege.

The interruptions come after a recent spate of mysterious drone incidents targeting airports and sensitive military locations in several European countries, including Germany and Denmark.

Suspicions have swirled over potential Russian involvement in increased drone activity across Europe, with tension high as the war in Ukraine drags through its fourth year.

Over the weekend, Belgian authorities reported drone activity over the Kleine-Brogel military base, where a number of US nuclear weapons are believed to be stored.

Belgian military intelligence said it was conducting an investigation into the sightings.

Defence minister Theo Francken on Monday refused to point the finger at Russia, but said that it appeared to be a coordinated operation carried out by “professionals”.

“They are trying to sow panic in Belgium,” Francken told local media.

“This is destabilisation,” he said.