UPDATE: The crash is being investigated as an act of terrorism, according to a German intelligence official familiar with the matter.

ORIGINAL: BERLIN (CBS NEWS) - At least nine people were killed and dozens injured when a truck plowed through a crowd at a popular Christmas Market in Berlin late Monday, police said.

Polizei Berlin confirmed the deaths on Twitter, although it’s still not clear what happened to the attacker or attackers.

The attack happened in Breitscheidplatz, a major square in the center of the German capital. Every year, the city of Berlin hosts a Christmas market there near the fashionable Kurfuerstendamm avenue. The attack happened at the foot of the landmark Kaiser Wilhelm memorial church, which was kept as a ruin after World War II. 

German police haven’t announced a suspect nor a motive in the attack. Bild newspaper posted a picture of a large Scania truck with its windshield smashed out on the sidewalk alongside the market.

However, several people in the U.S. intelligence community told CBS News that the situation in Berlin has all the hallmarks of a terror attack.

Officials here in the U.S. say it bears similarities to the recent terror attack in Nice, France, and is what terror groups have been calling for their followers to do.

German police have recently rounded up a series of people for planning attacks on Christmas markets, and even detained last week a 12-year-old Iraqi boy for attempting to set off a nail bomb in one of them.

Many in Germany have been fearful of a rise in terrorism since the country took in more than a million migrants and refugees last year, mostly fleeing conflict in the Mideast. 

German prosecutors were already investigating a 12-year-old boy who allegedly attempted to set off a nail bomb at a Christmas market in the southern city of Ludwigshafen last week.

The German-born son of Iraqi parents is alleged to have tried to set off the device at the Christmas market on Nov. 26, and again outside city hall on Dec. 5, Focus magazine reported, citing security sources.

In the second failed attempt, a passer-by spotted the backpack containing the device and reported it to authorities. Inside they found a glass jar packed with firecrackers with nails taped to it, Focus reported.

Police said it would have burned but would not have exploded.

Stephan Meyer, the parliamentary spokesman on security issues for Chancellor Angela Merkel’s conservative bloc, said the boy apparently had turned rapidly to Islamic extremism.

“This shows how quickly the radicalization of a young person, a child, can take place,” he said.

The attack in Berlin called to mind the brutal July terrorist assault in Nice, France, that saw 86 people killed and hundreds injured by an Algerian member of the Islamic State of Iraq and Syria (ISIS.)

In the Nice attack, officials said Mohamed Lahouaiyej Bouhlel deliberately drove a 19-ton truck into thick crowds on the French Riviera celebrating the country’s independence day.