A woman has shared gruesome images of her grandmother's savaged leg after a dog attack in South Auckland.

Kylee Watt posted the images on Facebook, saying her grandmother was attacked in Waiuku on Waitangi Day.

The photos show an open wound on the woman's leg, and her foot covered in blood.

A second photo taken later shows large bruises and a large gash on her shin.

"The owner and his mate just left her to bleed," the post said.

"The police and dog control won't do anything! Which is so NOT RIGHT."

The post has been shared on Facebook more than 4000 times.

A St John spokeswoman confirmed to the Herald that staff attended an incident about 1.15pm on Saturday involving a 68-year-old woman.

She was in a moderate condition, and they transported her to Middlemore Hospital

The Herald understands that the police were contacted about the attack once the woman was in hospital. They referred the incident to animal control services.

Auckland Council field animal management services manager Geoff Keber said the agency did not receive hear from the victim or her family after the attack.

"The team were advised indirectly about the attack... An animal management officer has been dispatched to the family address to get a clear understanding of what happened. Inquiries are continuing."

Keber said the council sympathised with the victim "and understand that an attack can be extremely distressing and frightening".