A six-year-old girl was attacked by a dog, at Pole Hill in Chingford, London on Saturday. The attack took place at 12:00 GMT.
The girl, who was with her parents, had her ear bitten off and sustained injuries to her neck and shoulder. She is now in hospital, awaiting surgery.
The police are now searching for the dog and its owner. The dog is thought to be a black-and-white bull terrier and its owner has been described as a white male with cropped blonde hair and between 38 and 40 years old.
"This was an appalling incident that left a young child with serious injuries which are likely to scar her for life," said Detective Sergeant Stuart Cheek of the Waltham Forest police.
"I would appeal to anyone who saw what happened, was in the area at the time of the attack, or has noticed anything since that might assist the investigation, to get in touch as soon as possible," he added.
"It is crucial that we find those responsible so that no-one else is put at risk by this dog and its owner," he concluded.