BRUSSELS (AP) -- Flights at Belgium's main international airport remained disrupted on Wednesday after drone sightings overnight forced it to close temporarily and Prime Minister Bart De Wever called a meeting with senior ministers to discuss safety concerns.

It was the first time that airport in Brussels has been shut down by drones. It comes after a series of unidentified drone flights over the weekend near a military base where U.S. nuclear weapons are stored.

Brussels Airport said delays and cancellations were still possible after the Tuesday evening shutdown "for safety reasons" and apologized, saying that "the safety of our passengers and staff remains our top priority."

De Wever convened a meeting of Belgium's National Security Council, which includes the country's defense, interior, justice and foreign ministers, for Thursday morning.

The operators of the drones in recent days have not been identified, but Defense Minister Theo Francken said that flights near the Kleine-Brogel air base on Saturday and Sunday nights appeared to be "a spying operation" aimed at "destabilizing" people.

Last month, several drones were spotted above another Belgian military base near the German border. The operators were not identified.

In recent months, drone incidents across Europe have forced airports to shut down for a time. A late evening drone sighting at Berlin's Brandenburg airport on Friday suspended flights for nearly two hours. It was not clear who was responsible.