A truck plowed through a Christmas market in Germany's capital on Monday evening, killing at least nine and injuring 50, a spokesman for the Berlin police said.
The incident happened at Breitscheidplatz, a public square in the center of Berlin. The driver's nationality wasn't known, but police said his truck appeared to have Polish license plates.
The driver attempted to flee but was apprehended by police, they added.
A passenger in the truck was among those killed, police spokesman Thomas Neuendorf said on German TV. It immediately wasn't clear how the passenger died, or the relationship to the driver.
t wasn't clear whether the truck veered into the holiday crowds on purpose or by accident. But local German media cited police who said initial indications pointed to an attack, not a traffic accident. NBC News could not immediately confirm those reports.
Witnesses said victims were crushed by the truck.
Last July, a truck driver killed 84 Bastille Day revelers in Nice, France, and injured more than 200, before he was shot dead by police. Officials said he had been planning the attack for months.
U.S. officials have long feared truck attacks on American soil. Permanent truck barriers were installed around government buildings nationwide after the 1995 truck bomb attack in Oklahoma City.
In November, the U.S. State Department warned American citizens to exercise caution at holiday festivals and outdoor markets while overseas in light of the heightened risk of terror attacks throughout Europe.
"While extremists have carried out attacks in Belgium, France, Germany, and Turkey in the past year, the Department remains concerned about the potential for attacks throughout Europe," the State Department said in a statement. "U.S. citizens should exercise vigilance when attending large holiday events, visiting tourist sites, using public transportation, and frequenting places of worship, restaurants, hotels, etc."
The Christmas market at Breitscheidplatz, close to the Kaiser-Wilhelm-Church, is just off the main shopping West Berlin district and is one of dozens Christmas markets in the city.