Bomb threats were reported earlier involving two inbound airliners at Brussels' main airport, Zaventem, as initially reported by Belgian state broadcaster VRT. Federal prosecutors said they had reason to take the threats "very seriously," according to the Belga news agency.

One airplane belonging to the Scandinavian SAS airline suspected to be affected by the threat landed at the airport, with all passengers disembarking safely. Another airliner heading for Zaventem belonging to the Moroccan Air Arabia Maroc was reportedly diverted to the French city of Toulouse. But it remained unclear whether this was the second airplane affected by the bomb alert.

Belgian media meanwhile said that some planes had been diverted to other airports.

Belgium still on high alert

Belgian Interior Minister Jan Jambon made a public announcement saying there was "no reason to panic." However, the Belgian capital is still tense after the devastating attacks earlier in the year.

On March 22, two Islamist attackers blew themselves up at the same airport, while a third assailant set off explosives at an underground station in central Brussels, killing more than 30 people in total.

Many of the attackers who carried out the November 13, 2015 attacks in Paris were also based in Belgium and may have had ties to the Brussels attackers.

A recent machete attack on a policewomen and repeated terror-related arrests throughout the country have kept Belgians on alert. The country is on its second-highest terrorism alert level, meaning that the authorities perceive the threat of an attack to be "serious, possible and likely."