SYDNEY, July 4 AAP - A Sydney police officer is in a serious condition after hitting his head hard on the road during a struggle with a youth he was trying to arrest.
Police say the 16-year-old became aggressive when the dog squad officer approached him at Macquarie Centre around 10pm on Monday.
It's alleged the youth then kicked the officer in the face, causing him to fall and hit his head on the road.
"I saw one police officer lying in the gutter, and another man lying down there injured on the floor," a witness told Nine.
"I couldn't see what happened, but the police officer seemed to be fairly badly injured."
The officer had stopped to question the boy after he noticed him acting suspiciously at the shopping centre in Sydney's northwest.
Two other police officers on the scene arrested the 16-year-old. He's been taken to hospital for assessment.
The injured officer remained in a serious but stable condition, Detective Superintendent John Duncan told reporters on Tuesday.
"He's conscious but it is going to be a long road to recovery," Det Supt Duncan said.
The 16-year-old is in custody and currently assisting police with their inquiries at Ryde Police Station.
He's likely to be charged later on Tuesday, Det Supt Duncan said.