A massive black truck plowed into a Christmas market teeming with revelers in west Berlin on Monday, killing at least 12 people, wounding dozens more and leaving Germans mourning a national tragedy during the holiday season.

The incident, described by the White House as an apparent “terrorist attack,” had echoes of the deadly truck assault in the French city of Nice in July, which killed 86 people and was claimed by the Islamic State. German Interior Minister Thomas de Maizière told Germany’s ARD national broadcaster: “I don’t want to use the word attack yet, although a lot points to one.”

German authorities late Monday were questioning a male suspect arrested several hundred yards from the site, who matched a description of the truck driver. A dead body was found in the passenger side of the truck, which had Polish license plates.

Two senior German officials briefed on the matter told The Washington Post that the suspect is believed to be a Pakistani national who arrived in February as an asylum seeker. If the man is confirmed as the culprit, it is likely to fuel an already-heated debate in Germany over Chancellor Angela Merkel’s decision to open the door last year to nearly 1 million migrants, most of them fleeing war in the Middle East.

The deadly incident occurred near the historic Kaiser Wilhelm Memorial Church in the Breitscheidplatz, a major public plaza. The bloodshed came at the height of activity at the Christmas markets, a cherished German tradition that draws locals and tourists to city squares for mugs of mulled wine, grilled sausages and regional sweets, as well as shopping at quaint stalls that sell handmade ornaments and other items.

1 of 32 Full Screen Autoplay Close Skip Ad × Photos from the scene: Truck rams crowd in Berlin Christmas market View Photos A massive black truck plowed into a Christmas market teeming with holiday revelers in west Berlin on Monday, killing nine people and wounding dozens more. Caption The suspect in the attack, 24-year-old Anis Amri, was killed in a shootout with police in Milan on Dec. 23. Dec. 23, 2016 Italian police officers stand next to the body of Anis Amri, the suspect in the Berlin truck attack, in a suburb of Milan. Reuters Buy Photo Wait 1 second to continue.

In Berlin, the festive scene turned into panic shortly after 8 p.m. Monday as the truck veered onto the sidewalk and crashed between market stalls, running 50 to 80 feet before stopping, according to witnesses. Some victims were pinned under its wheels while others were struck and tossed onto the pavement.

According to police spokeswoman Valeska Jakubowski, 12 people were killed and 48 were being treated at a hospital.

After the incident, the scene remained a horrific tableau of crushed wood, broken glass and blood. Lying near the truck was a fallen Christmas tree, its star toppled.

Government spokesman Steffen Seibert tweeted: “Terrible news from #Breitscheidplatz. Chancellor #Merkel is in touch with interior minister and gov. mayor.”

On the scene, first responders were carrying off people in stretchers Monday night as police with machine guns cordoned off the area.

“It’s terrible, just terrible,” said Berlin Mayor Michael ­Müller. He said it was up to authorities to establish the facts, adding, “We always hoped that we wouldn’t have this kind of situation in Berlin.”

Following a rash of arrests, plots and attacks, Germany — like much of Europe — has been bracing for a terror assault on Christmas markets. Security had been beefed up, with guards checking bags at entrance points. So far this year, German officials have arrested more than a dozen people suspected of involvement in terror plots,while two others have carried out small-scale attacks.

According to Germany’s DPA news service, the owner of the truck, Ariel Zurawski, told the Polish network TVN 24 that the vehicle was being driven by his cousin on Monday and was carrying steel parts to Berlin. But he said he had lost touch with his cousin around 4 p.m. It was not immediately clear whether the truck had been hijacked.

Officials said they were exploring all possible explanations for the deadly incident, ranging from terrorism to a horrific accident.

“We cannot make any clear statement about the causes or the background” of the incident, said Winfried Wenzel, a spokesman for the Berlin police.

In a statement, U.S. National Security Council spokesman Ned Price condemned “in the strongest terms what appears to have been a terrorist attack on a Christmas Market in Berlin, which has killed and wounded dozens.”

President-elect Donald Trump also denounced what he called a “horrifying terrorist attack in Berlin,” saying in a statement that Islamist terrorists and their networks “must be eradicated from the face of the earth, a mission we will carry out with all freedom-loving partners.”

Although Germany’s Bild newspaper reported that authorities were investigating the attack as a possible act of terror, two senior security officials who spoke on the condition of anonymity said it was too early to determine the motive.

The killings in Berlin came just hours after a gunman in Zurich opened fire in an Islamic center, wounding three people who were praying, according to news reports. Police were searching Monday night for the assailant, who had fled the mosque, according to the reports.

In Berlin, an elderly man who saw the bloodshed told the Berliner Morgenpost that the driver appeared to be targeting the market, turning off his lights as he steered toward the crowds. “It must have been on purpose because he didn’t have the lights on,” he said. “Then I just heard this loud bang and hysterical screams.”

Breitscheidplatz is one the busiest of the city’s famous Christmas markets. Witnesses said visitors were drinking traditional hot wine and taking in the lights and sounds of the market when they heard a loud noise.

“We were enjoying the Christmas markets and some mulled wine,” one witness, Emma Rushton, told CNN. “We heard a loud bang and we started to see to our left Christmas lights were being torn down.” At that point, she said, she saw a truck crashing through the crowd.

Following the incident, police said, witnesses reported that the driver fled the scene. The suspect, police said, was arrested near the towering Victory Column in Berlin’s sprawling central park known as the Tiergarten.

The incident occurred as Germans have had to endure a growing threat of terrorism. So far this year, the Islamic State has claimed responsibility for two attacks in Germany.

In July, a 27-year-old rejected Syrian asylum seeker detonated a bomb near the entrance to a music festival in the center of the southern German town of Ansbach, killing himself and wounding several people.

Earlier that month, an Afghan asylum seeker armed with an ax injured four people on a German commuter train in the Bavarian city of Würzburg.

In July, a mass shooting in a Munich mall that wounded 36 and left 10 dead including the perpetrator was carried out by a mentally disturbed youth and was unrelated to Islamist terror.

Authorities for months have feared that terrorists might target Germany’s famous Christmas markets.

German prosecutors last week said they were investigating an incident in which a 12-year-old boy allegedly plotted a nail-bomb attack at a Christmas market in the southern city of Ludwigshafen. According to German media, investigators said that they think the boy, who holds dual German and Iraqi citizenship, was guided by a member of the Islamic State.

In July, a Tunisian-born man drove a 19-ton truck along the beachfront in Nice, mowing down 86 people during French Bastille Day celebrations. The attack was claimed by the Islamic State.

Mekhennet reported from Dubai.

Correction: an earlier version of this article incorrectly spelled the name of the newspaper Bild and the Breitscheidplatz square, and said the attack occurred in east Berlin. It happened in west Berlin. The date of the attack in Nice has also been corrected. It occurred in July, not August.

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