Four people are reported to have died after a car was driven at high speed into a pedestrian zone in the southwestern German city of Trier.
Police have confirmed the deaths of two people, and at least 15 other people were seriously injured, before the vehicle was stopped by police, officials said.
German news site Bild is reporting that a total of four people have been killed.
Reuters is reporting that a baby is among the victims, although is had not been confirmed if the child has been injured or killed.
The driver, identified as a 51-year-old German man from the area, was arrested at the scene and the vehicle was impounded, Trier police spokesman Karl-Peter Jochem said, according to news agency dpa.
Footage from the scene showed people outside a shop apparently helping someone on the ground lying among scattered debris.
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“It was simply terrible,” mayor Wolfram Leibe told n-tv television after visiting the site on Tuesday.
Mr Leibe said the perpetrator “drove through the pedestrian zone, clearly at high speed, and killed several people and injured several, some of them seriously”.
The driver is being questioned by police, he said.
“I don’t want to speculate, but all of us are asking ourselves … what drives a person to do something like this?” Mr Leibe said.
“Of course I don’t have an answer to this question.”
The area was being kept shut down until at least Wednesday morning for police to collect evidence, but there was no longer any danger, Mr Leibe said.
Trier is about 120 miles west of Frankfurt, near the border with Luxembourg.
The city of about 110,000 people is known for its Roman gate, the Porta Nigra, which is near the scene of the crash, and as the birthplace of Karl Marx.