Utrecht, Netherlands — Three people were killed and nine injured in a shooting in the Dutch city of Utrecht, the mayor said Monday, adding that authorities were working on the basis of it being a terror attack.

“At this stage, we can confirm three deaths and nine wounded, three of them seriously,” Utrecht Mayor Jan van Zanen said in a video statement on Twitter.

The toll is likely to go up.

Dutch police said they were looking for a 37-year-old Turkish man in connection with the shooting. “The police ask you to watch out for 37-year-old Gokmen Tanis (born in Turkey) in connection with this morning’s incident,” a police statement said.

Authorities raised the terrorism threat to its highest level in Utrecht province, schools were told to shut their doors and paramilitary police increased security at airports and other vital infrastructure, and also at mosques.

Dutch Prime Minister Mark Rutte convened crisis talks, saying he was deeply concerned about the incident, which came three days after a lone gunman killed 50 people in mass shootings at two mosques in the city of Christchurch, New Zealand.

Earlier, the head of Dutch counter-terrorism said shots had been fired at several locations, without elaborating. Counter-terrorism units surrounded a house in Utrecht, Dutch television showed, but no one appeared to have been arrested.

Utrecht, the Netherlands’ fourth largest city with a population of around 340,000, is known for its picturesque canals and large student population. Gun killings are rare in Utrecht, as elsewhere in the Netherlands.

“A lot is still unclear at this point and local authorities are working hard to establish all the facts. What we already know is that a culprit is at large,” Counter-Terrorism Agency head Pieter-Jaap Aalbersberg told a news conference.

The Utrecht municipality said it advised “everyone to stay indoors until more is known. New incidents are not excluded.” The local hospital said it had set up a crisis center.

Mosques in Utrecht had shut for the day following the attack, the ANP news agency said. — Agencies