In Utrecht, Gunman Aboard a Tram Kills at Least 3

Three people died and nine were injured on Monday in a shooting on a tram in the Dutch city of Utrecht, which the authorities called a possible terrorist attack, and a manhunt was underway for a gunman who escaped the scene.

The Netherlands’ main counterterrorism agency raised its assessment of the threat in Utrecht province, just southeast of Amsterdam, to the highest level, and said it had activated a crisis team. The Dutch paramilitary police increased security at airports and other vital infrastructure points.

By midafternoon there had been no arrests, but the Utrecht Police said they were looking for Gokmen Tanis, 37, who was born in Turkey, and posted a security camera image of him online. They did not call him a suspect, but said he was “associated with the incident” and warned people not to approach him.

Unlike the police, the mayor of Utrecht, Jan van Zanen, referred to Mr. Tanis as a suspect.

“We are working on the assumption of a terrorist motive,” Mr. van Zanen said. “We think there is just one perpetrator, but we cannot exclude the possibly of there being several perpetrators.”

All the mosques in Utrecht were ordered evacuated, and security was increased at mosques elsewhere in the Netherlands. It was not clear whether those moves stemmed from any specific threat, or if they were a precaution in the wake of the attacks on mosques last week in Christchurch, New Zealand that killed 50 people.

Trauma helicopters were sent to the scene, the Utrecht Police said on Twitter, and trams in the city were shut down while the authorities investigated the attacker and searched for those responsible. The authorities urged people to avoid the area to allow aid workers to reach the site of the attack at October 24 Square.

The University Medical Center Utrecht opened a specialized disaster unit in response to the shooting. Prime Minister Mark Rutte interrupted a weekly cabinet meeting to monitor the situation, several news outlets reported.

Utrecht, about 25 miles from Amsterdam, has a population of about 330,000, and has been a center of Dutch culture and commerce for a millenium. Utrecht University is the largest in the Netherlands, and the city has multiple museums, a medieval old town, canals and the headquarters of the Protestant Church in the Netherlands.

Jimmy de Koster, a witness, told the television station RTV Utrecht that he was at the square, heard gunfire and saw a young woman, apparently wounded, lying on the ground.

“Four men walked very fast toward her and tried to drag her away,” he said. More shots were then fired, he said, and the men left.

The attack took place in the Kanaleneiland neighborhood in Utrecht, which is home to a large Muslim community, but it was not clear whether that influenced the decision of the gunman to open fire when and where he did.

Unlike Britain, Belgium, France and Germany, the Netherlands had not had a major terrorist attack in recent years. But the Dutch police said in September that they had foiled “very advanced” plans for a coordinated series of attacks, arresting seven men and seizing guns and bomb-making materials.

Pieter Jaap Aalbersberg, the national coordinator for antiterrorism and security, said the terror alert was limited to Utrecht province and that the authorities were debating whether to expand it to the country as a whole.

The Netherlands has one of the lowest rates of private firearms ownership in Europe, according to international studies, about 2.6 per 100 people, compared to more than one per person in the United States. Its rate of gun homicide, about .2 to .3 per 100,000 people each year, is fairly typical for Europe, and far below the United States rate of about 4 per 100,000 people.