At least 12 people were killed and 48 others injured after a truck drove into a Christmasmarket in a public square in Berlin, according to police.
The incident holds obvious similarities to the Bastille Day attack in Nice, France, this July, when a man drove a rented truck into a crowd, killing scores of people.
"Just now a truck just drove over the sideway at #Breitscheidplatz. Our colleagues report injured people. More information here," Berlin police tweeted.
Berlin police said a suspect was arrested after the incident but did not specify whether the person was the driver of the truck.
A male passenger in the truck died at the scene, authorities said. Berlin police confirmed later in a tweet that the man was a Polish citizen.
Police said on Twitter that they suspect the truck was stolen in Poland from a building site.
The investigation is ongoing, police said.
White House National Security Council spokesman Ned Price described the incident as an apparent "terrorist attack."
"The United States condemns in the strongest terms what appears to have been a terrorist attack on a Christmas market in Berlin, Germany, which has killed and wounded dozens. We send our thoughts and prayers to the families and loved ones of those killed, just as we wish a speedy recovery to all of those wounded. We also extend our heartfelt condolences to the people and government of Germany," the statement reads.
Price added that the U.S. has offered to aid Germany in the investigation.
"We have been in touch with German officials, and we stand ready to provide assistance as they recover from and investigate this horrific incident. Germany is one of our closest partners and strongest allies, and we stand together with Berlin in the fight against all those who target our way of life and threaten our societies," he said.
President-elect Donald Trump also released a statement about the incident, calling it "horrifying."
"Our hearts and prayers are with the loved ones of the victims of today's horrifying terror attack in Berlin. Innocent civilians were murdered in the streets as they prepared to celebrate the Christmas holiday," Trump said.
Trump went on to appear to tie the incident to ISIS.
"ISIS and other Islamist terrorists continually slaughter Christians in their communities and places of worship as part of their global jihad. These terrorists and their regional and worldwide networks must be eradicated from the face of the earth, a mission we will carry out with all freedom-loving partners," he concluded.