The threats were believed to be radioed in from the aircraft
Two planes have landed safetly at Brussels Airport in Zaventem after bomb threats were made against them.
There are reports the planes originated from Oslo and Stockholm.
It is believed both planes are now being inspected.
The threats, apparently radioed in from the aircraft to air traffic control, came from messages on Twitter according to Belgian newspaper HLN.
However, an airport police spokeswoman told Reuters no bomb alerts were in place - and that there was no problem at the airport.
Federal prosecutors are taking the threats seriously and have taken a number of security measures, broadcaster VRT said.
Last March, Islamist bombers killed 32 people in suicide attacks at Brussels Airport and a metro station.
Belgian media said some planes had been diverted to other airports.
A passenger on the Oslo plane, Bart Raes, tweeted to say the threat was made "20 minutes before landing".
Bommelding op mijn vlucht van Oslo naar @BrusselsAirport 20 minuten voor landing bij piloot binnengelopen.— Bart Raes (@brtraes) August 10, 2016