Bomb alerts have been reported on two passenger jets due to arrive at Brussels airport.
The alerts were reportedly radioed in from the aircraft to air traffic control.
The threats came from messages on Twitter, according to Belgian newspaper HLN.
Both planes have now landed safely.
The planes were both run by the Scandivian airline, SAS, one came from Oslo in Norway and the other from Arlanda in Sweden.
Belgian journalist Bart Raes, who was on one of the flights, tweeted to say the pilot had entered the cabin 20 minutes before landing, saying there may be a bomb on the plane.
He asked people to remain in their seats and they waited for approximately 10 minutes after they landed safely.
Mr Raes said he left the plane safely and was now in the Arrivals hall at the airport.
He told HLN everyone was "shocked" when the pilot told them about the threat.
He said: "We saw nothing, no fire or police.
"After waiting for awhile, we were allowed to get off. So it was a false report, I suppose.
"All passengers are already on their way home now or wait for a connecting flight".
A spokesman for the federal prosecutor, Eric Van der Sypt, told Belgain broadcaster VRT there was a threat deemed "serious enough to take measures".
It comes as tensions in the country are already running high following a major terror attack at the same airport in March killing 16 people.
The two nail bombings were part of three suicide attacks co-ordinated to go off at the same time across the city.
The city has had several false alarms in recent months, including an incident in the city centre last month when a Physics student conducting an experiment was cornered by police after he was spotted wearing a long coat with wires sticking out.
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