Both NATO and the European Union have been on high alert following a string of airspace violations, thought to be from Russia, in recent weeks.
The airspace over Brussels Zaventem Airport has been closed following reports of a drone flying over the airfield, the public service broadcaster VRT reported on Tuesday night.
All departing and arriving flights were temporarily suspended earlier in the evening after a drone sighting was reported above the international airport. Brussels Zaventem Airport briefly reopened its airspace, before closing it again following a second drone sighting, VRT wrote.
Liège Airport, where planes that couldn't land at Brussels Airport were intially redirected to, also closed following a separate drone sighting incident, the public service broadcaster added.
Earlier in the day, a spokesperson for skeyes, the public company responsible for Belgium's civil airspace, said the first drone sighting happened at around 8 pm local time, prompting flights to be diverted to other airports such as Ostend-Bruges and Charleroi Brussels South.
Both NATO and the European Union have been on high alert following a string of airspace violations, thought to be from Russia, in recent weeks.
NATO issued a warning to Moscow at the end of September, saying it would use all means to defend against any further breaches of its airspace after the downing of Russian drones over Poland and Estonia's report of an intrusion by Russian fighter jets.
The 10 September incident in Poland was the first direct encounter between NATO and Russia since its full-scale invasion of Ukraine began in early 2022.
Estonia said three Russian MiG-31 fighter jets entered its airspace for 12 minutes on Friday without authorisation, a charge that the Kremlin has rejected.
The incidents caused widespread consternation among leaders across Europe, raising questions about the alliance's preparedness against growing Russian aggression.
Following the violation of Polish airspace, NATO Secretary General Mark Rutte announced the formation of the Eastern Sentry programme, which aims to deter further Russian incursions and show solidarity with Poland.
"We see drones violating our airspace. Whether it was intentional or not, it is unacceptable. The allies have expressed full solidarity with Poland. It is crucial to counter aggression and defend every member of the Alliance," the NATO chief said.