More than 20 people have been injured after a vehicle drove through a holiday parade in the US state of Wisconsin, according to police.

The incident happened in Waukesha, which is about 20 miles west of central Milwaukee, just before 5pm on Sunday.

In footage on social media, the red vehicle appeared to speed towards marchers from behind, with police opening fire on it as it crashed through street barriers.

The city's police chief Dan Thompson said a "suspect vehicle" had been found.

He added: "We have a person of interest that we are looking into at this time", although he did not say whether the person had been arrested.

Angelito Tenorio, who was at the parade, told the Milwaukee Journal Sentinel: "As we were walking back in between the buildings... we saw an SUV cross over, just put the pedal to the metal and just zooming full speed along the parade route.

"And then we heard a loud bang, and just deafening cries and screams from people who are struck by the vehicle."

Also, Carroll University has said its campus in Waukesha is on lockdown, saying this is due to "an ongoing incident" without giving further details.