A lorry ploughed through a Christmas market in Berlin, killing at least nine and injuring 50, in what police said was probably a deliberate attack.
A suspect was arrested, police said. They are thought to be the driver. The co-driver "died on the spot", police added.
Citing police at the scene, German media said first indications pointed to an attack on the market, situated at the foot of the ruined Kaiser Wilhelm memorial church, which was kept as a bombed-out ruin after World War Two.
Eyewitnesses reported that the lorry entered the market "at some speed - perhaps as high as 40mph", knocking down stalls before eventually coming to a standstill.
Video showed destroyed hoardings and stalls.
Mike Fox, a tourist from Birmingham, said that the lorry missed him by only about three meters as it drove into the market, tearing through tables and wooden stands.
"It was definitely deliberate," he said, adding that he helped people who appeared to have broken limbs, and that others were trapped under Christmas stands.
Another, Emma Rushton agreed that "it wasn't an accident."
She told Sky News: "It was going at 40mph through the middle of the market. There was no way it could have come off the road and it showed no signs of slowing down."
She added: "There were lots and lots of people, this is Monday evening, people had finished work. There were tourists there."
Jan Hollitzer, deputy editor in chief of the Berliner Morgenpost said: "I heard a big noise and then I moved on the Christmas market and saw much chaos...many injured people," "It was really traumatic."
A photo posted by his newspaper showed damaged tables and stalls.
Police cars and ambulances converged quickly on the scene as a huge security operation unfolded. The fate of the driver of the truck was not immediately clear, but Bild newspaper said he was on the run.
The incident evoked memories of the attack of the July attack in the French town of Nice when a Tunisian-born man drove a 19-tonne truck along the beach front, mowing down people who had gathered to watch the fireworks on Bastille Day, killing 86 people. The attack was claimed by Isis.
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