The force said the boy’s family had been informed and were being supported by specialist officers.
Det Insp Joe Davenport said: “If you were in the area at the time and saw what happened, or think you may have captured any part of what happened on dashcam or mobile phone, it’s vital you get in touch.”
Scribers Lane is a long and busy road, surrounded by houses, shops and local schools, in the suburb of Hall Green.
The attack is believed to have taken place near the railway bridge, which is next to Trittiford Mill Park.
