The vehicle is said to have driven into the crowd right behind a school band.
The police arrested one person.
The background to the incident is still unclear.
Waukesha - In the US state of Wisconsin, a car sped into a Christmas parade, killing several people.
The police spoke after the incident on Sunday in Waukesha, a suburb of the city of Milwaukee, of "some fatalities" without first specifying.
According to the fire department, a total of more than 20 injured people were admitted to hospitals, including twelve children.
The police arrested a person, said local police chief Dan Thompson.
There is no further danger.
The exact background was initially unclear.
Fatal SUV accident in the USA: Video should show the incident
According to the police, a red SUV broke the barriers during the Christmas parade.
"The vehicle hit more than 20 people," said Thompson.
"Some of them were children and there were some fatalities." According to authorities, a police officer shot the car during the incident to stop it.
According to information from the
Milwaukee Journal Sentinel
, camera recordings show that the SUV raced into the parade right behind a band of schoolchildren.
Eyewitness Angelito Tenorio told the newspaper that the car had sped at "full speed" across the street where the parade was taking place.
"Then we heard a loud bang and deafening screams from people who were hit by the vehicle."
Wisconsin Governor Tony Evers said he and his wife would "pray today for Waukesha and all the children, families and community members affected by this pointless act."