One person has died and there are multiple people injured after a shooting on a tram in the central Dutch city of Utrecht, according to police.
Authorities immediately raised the terror alert for the area to the maximum level and said they are considering the possibility of a "terrorist motive" in the attack.
Dutch military police went on extra alert at Dutch airports and at key buildings in the country as the Utrecht manhunt took place.
Police, including heavily-armed officers, flooded the area after the shooting on Monday morning on a tram at a busy traffic intersection in a residential area.
Anti-terror officers gathered in front of a block of flats close to the scene. Authorities say that a suspect is still on the run following the shooting.
Utrecht police said trauma helicopters were sent to the scene and appealed to the public to stay away.
Dutch Prime Minister Mark Rutte called the situation "very worrying" and the country's counter-terror co-ordinator said in a tweet that a crisis team was meeting to discuss the situation.
Police spokesman Bernhard Jens said no-one had been detained yet in the shooting and one possible "explanation is that the person fled by car". He did not rule out the possibility that more than one person was involved in the attack.
"We want to try to catch the person responsible as soon as possible," Mr Jens said.
The country's anti-terror co-ordinator raised the threat alert to its highest level around Utrecht. Pieter-Jaap Aalbersberg said the "threat level has gone to 5, exclusively for the Utrecht province".
Police in Germany say they have upped surveillance on the country's border and are on the lookout for the gunman.
Heinrich Onstein, a spokesman for the federal police in the border state of North Rhine-Westphalia, said additional police had been added to watch not only major roads, but also minor crossings as well as railway routes.