Dutch authorities suspect one person was killed in a shooting on a tram in the city of Utrecht on Monday, a police spokeswoman said.
Separately, a reporter for Dutch national broadcaster NOS said a white sheet had been placed over a body near the tram where the shooting took place.
Prime Minister Mark Rutte said he was "deeply concerned" and cancelled his weekly coalition talks.
The shooting took place around the 24 Oktoberplein junction at about 10:45 local time (09:45 GMT). Three helicopters have been despatched.
Security services have reportedly told Utrecht's University Medical Centre to open the dedicated emergency ward to help care for the injured.