A Melbourne mother-of-two has been left with a badly mauled arm after she was attacked by a dog she was trying to help.

Louise Gavin approached a German Shepherd wandering near her Hampton Park home in the city's southeast as she was worried it would be hit by a car.

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But her concern for the dog quickly changed after she leaned down with her arm.

Louise Gavin approached a German Shepherd wandering near her Hampton Park home. Credit: 7NEWS

"I didn't try and touch it. I just dropped my hand down and went 'hello,' to let it sniff me and see if it was going to be okay," Gavin told 7NEWS.

Chevron Right Icon 'I didn't try and touch it.'

The mother said the dog then jumped and went for her face and neck.

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"Until I broke free, I honestly thought the dog was going to kill me," she said.

Chevron Right Icon 'I honestly thought the dog was going to kill me.'

After the dog released her arm, Gavin ran bleeding to the nearby Hampton Park Vet Hospital.

The mother said the dog jumped and went for her face and neck before grabbing her arm. Credit: 7NEWS

Veterinarian Dr Cameron Rain said the bite marks were close to her elbow joint and were quite serious.

Chevron Right Icon 'Until I broke free, I honestly thought the dog was going to kill me.'

The dog was seized by Casey Council as rangers decide what happens next, but Gavin, who is a dog owner herself, doesn't necessarily want the German Shepherd put down.

Instead, she wants the owners to make sure the animal's yard is more secure and dogs are better trained to be around people.

Veterinarian Dr Cameron Rain said the bite marks were close to her elbow joint. Credit: 7NEWS

"A dog should never be so unsocialised that it is completely unapproachable," she said.

Gavin has been left with multiple stitches, on antibiotics and in a sling.