At least 12 people were killed and 48 injured when a truck ploughed into a crowd at a Christmas market in Berlin on Monday evening.
One suspect was taken into custody and another person in the truck died as it crashed into a crowd of people at the market.
An investigation is underway to find out whether the incident was terror-related.
Berlin police on Tuesday tweeted that the truck was "intentionally" steered into the crowd.
Unsere Ermittler gehen davon aus, dass der LKW vorstzlich in die Menschenmenge auf dem Weihnachtsmarkt am #Breitscheidplatz gesteuert wurde— PolizeiBerlinEinsatz (@PolizeiBerlin_E) December 20, 2016
German officials stated that there was no indication of "further dangerous situations in the city near Breitscheidplatz," where the attack took place.
Social media carried messages from witnesses.
A truck ran into a crowded Berlin Christmas market outside the Kaiser Wilhelm Memorial Church. https://t.co/nZiw6pb31h— Julie Lenarz (@MsJulieLenarz) December 19, 2016
"I just saw this huge black truck speeding through the markets crushing so many people and then all the lights went out and everything was destroyed," an eyewitness, Trisha O'Neill, told the Australian Broadcasting Corporation.
O'Neill added that there was "blood and bodies everywhere."
German Chancellor Angela Merkel reacted quickly to the tragedy, with spokesperson Steffen Seibert tweeting: "We mourn the dead and hope that the many people injured can be helped."
The arrival of 890,000 refugees last year has polarised Germany and misgivings run particularly deep in the ex-communist east, even more so following a series of Daesh-linked attacks in Europe that were carried out by asylum-seekers.
The incident occurred five months after an attack in France when a Tunisian-born man, Mohamed Lahouaiej Bouhlel, drove a 19-tonne truck along the beachfront in Nice, mowing down people who had gathered to watch the fireworks on Bastille Day, killing 86 people.
Daesh claimed the Nice attack.