Jan de Jong, director of the NOS, told national radio "Someone got into the building" and added that the man had been taken into custody.
De Jong said it was unclear how the man got through tight security in the building and into the editorial offices.
Police didn't immediately return calls seeking comment, and calls to NOS offices in Hilversum went unanswered Thursday night.
The evening edition of the NOS news wasn't broadcast. Police quickly surrounded the building in Hilversum and evacuated staff, according to media reports. There were no reports of any shots being fired in the building.
The NOS 1 channel was still off-air with a screen reading: "Please be patient" in Dutch, and the broadcaster said on its website that police were searching the building.
Hilversum is about 20 kilometers (12 miles) east of Amsterdam.
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