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).

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, a spokesperson 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.

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.

A total of eight trauma teams have been made available, both for adults and children, dpa reported.

“Postponable operations that had not yet begun were immediately removed from the operation plan in order to create additional operating capacity,” the university hospital told dpa.

The capacities in the intensive care units have also been increased.

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.