A 9-year-old boy was left with what police are calling "life-altering" injuries after an unleashed dog attacked him at a Toronto playground.

The horrific attack happened at about 10:15 a.m. Saturday at Little Norway Park, according to the Toronto Police Service.

Police say a woman was inside the playground with a dog that was not on a leash.

A man with his son approached the playground area and the dog charged toward the boy through an open gate, police said.

The dog bit and dragged the child to the ground, according to police and a CBC report.

The woman and the boy's father attempted to get the dog to release the child.

When the dog finally let go, the woman took off from the park with her pet.

Emergency crews took the child to the hospital with serious injuries. He was expected to survive, but police called his injuries "life-altering."

Police describe the woman as 30 to 40 years old.  She was about 5'10" with a large build and dark hair worn in a ponytail.

She was last seen wearing glasses, a blue winter jacket and black pants. 

The dog was a mix of black, tan and white. It was wearing a black hooded jacket and a chain collar. 

Investigators were asking for the public's assistance to identify the dog and its owner because of a concern for public safety.