A heroic eight-year-old boy has saved his six-year-old sister after a pit bull launched a terrifying attack.

The unprovoked dog attack saw Michigan girl Lillian Chitwood, aged 6, left with savaged scars from bites to her face and neck.

The attack could have been fatal, had her older brother Nicholas, 8, not stepped in.

At the end of June, Lillian's mom says a fully grown pit bull dog broke out of a neighbour's yard and into the one the one where Lillian was playing in.

Nicholas' quick actions saw him kick the dog while getting his sister to safety and keeping her out of the way after the animal had bitten down on her face and neck.

The attack left the six-year-old little girl with extensive nerve damage and it's thought she might require further medical attention.

The children's mother Rebecca Chitwood told news station WNEM: "When I got the call, I just dropped everything and sped all the way to the hospital."

She added that she was told over the phone her daughter had been attacked by a dog, but not told the extent of it.

She continued: "To me, that could mean anything. It could be a couple of puncture wounds, it could be what she's experiencing now, it could've been even worse."

Relatives said Nicholas 'jumped into action' to save his sister after hearing her scream as his mother spoke of his bravery.

She said: "He jumped on the dog and pulled it off her and continued to kick it until her grandpa came to help.

"He was just trying to save his sister. He heard her let out a scream and… he jumped into action."

Speaking after the incident, Nicholas revealed to WNEM his reason for diving in against the fierce dog as he said: "I didn't want her to die."

Sister Lillian added: "It was hard, but I’m thankful for my brother to help me. Because if he didn’t, I would be dead by now."

After the attack the dog was put down by local authorities, and the family has now launched a GoFundMe page to help raise money to support her healthcare expenses for Lillian.

The page description reads: "On June 30, my 6 year old daughter was at grandma and grandpa's house innocently playing in their backyard when the neighbours' pit bull got out of their fence and came and attacked my daughter.

"The dog was NOT provoked. We were transported to university of Michigan for extensive surgery."

It continued: "The road ahead for my daughter is going to be long one, and numerous trips to University of Michigan which is a few hours away.

"This will require time off of work, and numerous medical bills for who knows how long, not to mention the mental aspect of this traumatizing experience for my baby girl! Any and all donations are much appreciated."

Currently the page has raised over $12,000.