Three people have been killed following a shooting on a tram in the central Dutch city of Utrecht, the city's mayor says.
Nine others were injured in the incident which police say appears to be a terrorist attack.
Police are looking for a 37-year-old Turkish man named 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.
"We cannot exclude a terrorist motive," Dutch anti-terrorism co-ordinator Pieter-Jaap Aalbersberg told a news conference on Monday.
"A lot is still unclear at this point and local authorities are working hard to establish all the facts," Mr Aalbersberg said.
He added that there had been shootings at "several locations", but did not elaborate on where these were.
Prime Minister Mark Rutte has said the incident was "deeply disturbing".
"An act of terror is an attack on our civilisation [and] on our tolerant and open society," he said.
Counter-terrorism police earlier surrounded a house near the 24 Oktoberplein junction, where the tram attack took place, but no arrests appear to have been made.
Meanwhile, the threat level has been temporarily raised to its highest point in the province of Utrecht.
Utrecht University has closed all of its buildings and trains are not allowed to run into the city's central station.
Paramilitary police have also been sent to airports and mosques amid increased security concerns.
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Source: bbc