At least 20 people were injured when a car drove into a crowd in Munich on Thursday, police said, as the southern German city prepares for a top-level security conference due to be attended by U.S. Vice President JD Vance and Ukrainian President Volodymyr Zelenskiy.

The Bild newspaper said police would have to establish whether the driver of the Mini Cooper had deliberately driven into the crowd or mixed up the accelerator and brake.

Police said on X they had detained the driver and did not consider him to pose any further threat, but declined to comment on whether it was an accident.

"At least 20 people injured, some seriously and critically," a spokesperson for Munich police said.

The Munich Security Conference starts on Friday and senior officials, including Vance and Zelenskiy, were arriving later on Thursday.

A large-scale police operation was underway near the city's central train station.

"One person is lying on the street and a young man has been taken away by the police. People are sitting on the ground, crying and trembling," a reporter for the local BR broadcaster wrote in a post on X.

The incident appeared to have affected people participating in a demonstration linked to a strike organised by the Verdi union, according to the broadcaster.

The union said it did not have any information on the incident.

Police set up a gathering point for witnesses in the Loewenbraeukeller, one of Munich's oldest beer halls.

The incident occurred around 1.5 kilometres (1 mile) from the security conference venue.

Security has been in sharp focus in Germany ahead of a federal election next week and following a string of violent attacks.