A young girl has undergone plastic surgery after being bitten on the face during a dog attack, with police now searching for the owner who fled the scene.

Little Hyacinth was left with horrific facial injuries after the attack at Gipps Street Recreation Reserve in Claremont Meadows, in western Sydney, on Saturday afternoon.

“I’ve pulled her hand away and realised that her lip and her nose and all of that has been bitten. It was very much a shock,” her mother Jade Dyer said.

The four-year-old needed reconstructive surgery following the attack by a large American pitbull.

Making matters worse, the dog’s owner left the park without providing any details or waiting for police to arrive.

“The people just up and left without waiting for police or giving any type of details,” Dyer said.

Police are investigating the incident, saying the unknown owner of the dog spoke to the girl’s family before leaving the scene.

The attack happened at a park packed with young children and families enjoying the long weekend.

“That’s not something you want to hear, especially being down here and so close to the park,” one local said. “We’ve all got young kids.”

Hyacinth’s family say plastic surgeons were happy with how Sunday’s operation went, but admit they don’t yet know whether she’ll suffer permanent scarring from the attack.

7NEWS has chosen to blur images of the owner but are confident of catching up with him to get both sides of the story and determine whether the animal had any history of being dangerous.

“Please come forward,” Dyer pleaded. “I don’t want you taking your dog to the same park again and having it [happen] to another child.”