A Perth woman has needed surgery on her arm after she was attacked by a savage pitbull near her home in Swan View on Friday.

Alison was walking her own dog, Twiggy, when the other dog, which had no owner nearby and no collar, clamped on to her.

The terrifying ordeal lasted almost five minutes.

Neighbours risked their own safety when they heard screams and ran to help.

Witness Nathan Ashby said the screams “ were blood curdling, like shriek"

Camera Icon Alison’s injuries. Credit: 7NEWS

By the time help arrived the pitbull had punctured Alison’s skin, torn the muscle, and left flesh hanging off her arm.

Alison said she was walking Twiggy on The Elbow when the dog crossed the railway line.

She was taken to Midland Hospital before being transferred to Royal Perth Hospital where she had surgery

Twiggy was also injured, suffering wounds to his stomach.

He has been prescribed antibiotics and painkillers and may also need surgery.

The family says they called police but haven't been able to contact the ranger.

Coincidentally, the patient recovering in the hospital bed next to Alison was attacked by a dog in nearby Midland a week before.

She was too upset to speak to 7NEWS on camera but said she needed stitches and is still on antibiotics.