Sydney boy injured, didn't stop for cops

A 15-year-old boy has serious injuries after he failed to stop on his trail bike for police in Sydney's west.

Police say the boy crashed into a Lexus sedan a short time after officers tried to stop him on Leabons Lane in Seven Hills around 4.30pm on Thursday.

He was been taken to the Children's Hospital at Westmead with leg and head injuries, an ambulance spokesman says.