Utrecht (Netherlands): A gunman killed three people and injured nine when he opened fire aboard a tram in a square to the west of the Dutch city of Utrecht on Monday in what authorities described as a possible terror attack, officials said.

Jan van Zanen, the Mayor of Utrecht, said in a television broadcast that a terrorist motive to the attack could not be ruled out after police named the suspect, reports Efe news.

"The police asks you to look out for the 37-year-old Gökmen Tanis (born in Turkey) associated with the incident this morning at the 24 Oktoberplein in Utrecht," police said, adding: "Do not approach him."

Police shared an image of the suspect apparently taken aboard a tram minutes before the attack was reported and urged members of the public in Utrecht to remain indoors and to report anything suspicious to a helpline.

The shooting took place at 10.45 a.m. in 24 Oktoberplein, a busy junction underneath a highway bridge.

Police said they had found a red Renault Clio car they had been looking for in connection to the attack.

The Dutch counter-terrorism and security unit NCTV was involved in the investigation.

"NCTV is monitoring the situation in Utrecht. In close contact with local authorities. We cannot rule out a terrorist motive. Crisis team is activated," said Pieter-Jaap Aalbersberg, the NCTV's national coordinator.

He said the suspected shooter had fled the scene and remained a fugitive, adding that the terror threat level in the province of Utrecht, in central Netherlands, had been raised to five, the highest possible category, meaning a terrorist attack was "expected imminently".

Netherlands broadcaster NOS said one of its reporters had seen a person lying immobile under a white sheet, an image later confirmed by television footage.

An eyewitness told NOS that an injured woman had come running out of the tram with blood covering her hands and on her clothes.

"I brought her into my car and helped her," the witness said. "When the police arrived, she was unconscious."

Television footage showed emergency services treating an injured person next to a car as a medical helicopter landed nearby.

The alert level, which was activated for a period of at least 18 hours, applied only to the Utrecht province, Aalbersberg said.

Armed police were deployed to the scene and security presence was boosted at the train stations and airports across the country.

Van Zanen said it was "a horrible and major incident in which victims have fallen".

"I am in close contact with the police and the public prosecutor. An initial assessment has already been undertaken. The assessment can confirm that the police and public prosecutor are currently looking for the person responsible."

Dutch Prime Minister Mark Rutte cancelled a government meeting in light of the events, which he described as a "worrying situation".

Police said witnesses had seen a man take a weapon out and start shooting continually and at random before fleeing the scene.

Utrecht is the fourth-largest city in the Netherlands located just 40 km to the southeast of the capital Amsterdam.