The main terminals at Amsterdam's Schiphol Airport were evacuated following a bomb threat on Monday, military police said.
They declined to confirm reports that the alert had been caused by a man in a lavatory.
We have evacuated the terminals and are investigating the report of a bomb. The area has been sealed, said Robert van Kapel from the Dutch military police unit at the airport.
Security has been increased at the airport.
A man had called the military police, said he was in the airport and claimed he had a bomb, said military police spokesman Martijn Peelen.
The military police declined to confirm local media reports that the man with the bomb was in a lavatory.
Terminals 1 and 2, the international terminals, were evacuated, Schiphol airport said.
Military police with automatic weapons were patrolling the area, a bomb squad had arrived, and hundreds of people were waiting outside the airport. Ambulances and fire trucks were on standby outside the airport.
At least a dozen flights were delayed, Schiphol's website showed.
A spokesman at state-owned Schiphol Group said they were studying whether the bomb threat would lead to cancellations.
Schiphol is one of Europe's busiest airports with around 40 million flight per year.
Train traffic, which runs under the airport in a tunnel, was not affected, a spokesman for rail network operator ProRail said.
(Additional reporting by Amsterdam Newsroom)