Bomb threats have been reported on two planes landing at Brussels airport in Zaventem, but one plane landed safely, Belgian state broadcaster VRT reports.
However, an airport police spokeswoman said no bomb alerts were in place and that there was no problem at the airport.
VRT said one of the planes, which was flying from Oslo, landed safely.
Federal prosecutors are taking the threats seriously and have taken a number of security measures, VRT said, citing prosecutor Eric Van der Sypt.
A reporter at Belgian broadcaster Woestijnvis/Proximus TV, Bart Raes, tweeted that he was on the flight from Oslo and that the pilot had received the bomb threat 20 minutes before the plane was due to land.
Raes said that passengers were informed of the threat and had to wait 10 minutes before being allowed to leave the plane after it landed.
Belgian media said some planes had been diverted to other airports.
Last March, Islamist bombers killed 32 people in suicide attacks at Brussels airport and a metro station. Many of those who carried out last November's attacks in Paris, which killed 130 people, were based in Belgium.