The mayor of Utrecht, Jan van Zanen has said three people were killed and nine others injured in Monday morning shooting at a tram in the central Dutch city.
Police said they are looking for a 37-year-old man of Turkish origin identified as Gokmen Tanis, and have warned people not to approach him.
Schools have closed and security has been increased while counter-terrorism police work to find the gunman who has been on the loose since driving away from the crime scene.
At a news conference on Monday, Dutch anti-terrorism co-ordinator Pieter-Jaap Aalbersberg said “We cannot exclude a terrorist motive.
“A lot is still unclear at this point and local authorities are working hard to establish all the facts.”