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A suspect is in custody after one person was killed and others injured when a car rammed into a crowd in the western German city of Mannheim, police say.
They asked the public to stay away from the downtown area and remain in their homes after the incident early on Monday afternoon (late Monday night AEDT). Several people were injured, he said, but police can't yet specify how many or how badly.
Police spokesperson Stefan Wilhelm said a driver drove into a group of people in Paradeplatz, a pedestrianised street in Mannheim, killing one person.
He said "several" people were injured but police can't yet specify how many were hurt and how badly they were hurt.
"We can confirm that one perpetrator was arrested," he said.
"We can't yet give information on whether there were further perpetrators."
Earlier, Wilhelm said the incident had been reported as "a life-threatening deployment situation".
Paradeplatz, a major square in the downtown area, lies at the end of a pedestrianised street in Mannheim, which has a population of 326,000 and lies 85 kilometres south of Frankfurt.
Images from the scene showed parts of the downtown area were cordoned off, with a heavy police presence and helicopters hovering above. Yellow ambulances were lining up outside the cordon.
Mannheim University Hospital says it has prepared everything for a possible mass casualty incident, German news agency dpa reported. The hospital has implemented its disaster and emergency plan to prepare for the care of the injured.
Authorities pushed an alert on the Katwarn app telling people in Mannheim to avoid the city's downtown area due to a big police deployment.
Katwarn is used by officials to communicate information about major emergencies such as thunderstorms, militant attacks or fires.
Across Germany, lots of people took a long weekend off to celebrate carnival, including Rose Monday, when many cities hold parades. Mannheim's street parade already took place, on Sunday.
German Interior Minister Nancy Faeser canceled her participation in the carnival street parade in Cologne due to the events in Mannheim.
"The focus is now on saving lives, treating the injured and the initial investigations by the authorities in Mannheim," an interior ministry spokesperson told dpa.
While police would not immediately characterise Monday's incident as an attack, cars have been used as deadly weapons in several acts of violence in recent months.
Last month, a two-year-old girl and her mother died two days after they were injured in a car-ramming attack on a labour union demonstration in Munich.
A 24-year-old Afghan man who came to Germany as an asylum seeker was arrested immediately after the attack, and prosecutors said he appeared to have had an Islamic extremist motive.
And last year, six people were killed and more than 200 injured when a car slammed into a Christmas market in eastern Germany city of Magdeburg. The suspect, who was arrested, is a 50-year-old doctor originally from Saudi Arabia who had expressed anti-Muslim views and support for the far-right, anti-immigrant Alternative For Germany party.
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