National broadcaster NOS said the attack could not immediately be attributed to terrorism.
Police launched a manhunt after the attack, which took place on a busy shopping street near the city's historic center. The area was cordoned off and dozens of police and ambulances were on the scene.
"We have an extensive investigation into the stabbing incident on the Grote Marktstraat," police said in a statement.
Police could not be reached directly for further comment.
National broadcaster NOS, quoting "varied sources," said: "At this moment there is no indication of a terrorist motive."
Police said they were seeking a man aged 45-50 in connection with the incident, and described him using a Dutch term often applied to people of North African descent.
The man was wearing a shawl, a black jacket and a grey tracksuit, they said.