A six-year-old boy is in "critical condition" after a car rammed into a crowd at a festival in Pennsylvania.

A woman in a wheelchair and another adult were also injured in the horrific incident, Harrisburg Police Commissioner Thomas Carter told ABC.

According to the Dauphin County District Attorney's Office, the driver of the vehicle is in custody.

The red minivan drove through the KIPONA Festival, which takes place every year during the Labour Day weekend, at 6pm on Monday night.

The three-day festival was coming to an end when the car drove around barricades before hitting people in the crowd on South Front Street.

Lottie Beauverd, a shopkeeper at the festival, told ABC: "This car came flying down through here fast.

"Not yelling or anything, but just flying down through this."