A family dog that turned on a five-year-old boy and bit him on the neck will be put down, NSW Police say.

The child was bitten on the left side of his neck at a home in Lake Macquarie in the NSW Hunter region on Sunday afternoon.

He was treated at the scene before being airlifted to The Children’s Hospital at Westmead in Sydney. He was expected to have surgery.

NSW Police said they were told the two-year-old dog – described as a Rottweiler-type breed – would be euthanised.