An Australian girl who spent three months in a coma battling an incurable brain tumour has tragically died overseas.

Annabelle Nguyen, 5, was taken to Mexico by her parents three years ago in a desperate attempt to save her after she was given less than a year to live.

The Perth-based family had recently launched a desperate appeal to collect funds to bring their daughter home as they said they couldn't afford to bring her back to Australia.

However, the young girl lost her brave fight to diffuse intrinsic pontine glioma (DIPG) on Wednesday.

'With our broken hearts, our Annabelle went to GOD's hand peacefully in my arms this morning. She is now free and be a normal girl again,' the family shared on Facebook.

A day earlier the family shared that Annabelle needed blood transfusions and was receiving brain-stem testing.

The world cancer community has heavily critcised the expensive and secretive Mexican clinic, the Daily Telegraph reported.

Families are charged around $30,000 per round of treatments which are required every month to six weeks.

Annabelle's parents Sandy and Trung Nguyen have spent in excess of $500,000 on treatment and were forced to sell their home.

Mother Sandy Nguyen told Daily Mail Australia in June that the family have 'nothing left' and would have needed $200,000 for a medical flight to bring her back to Australia.

'We have exhausted our funds,' she said. 'We have nothing...absolutely nothing left.'

Annabelle was first diagnosed with a brain tumour known as Diffuse Intrisic Pontine Glioma in 2015 and was told there was no cure.

After a global search for help, the parents took Annabelle to Mexico for expensive treatment.

Parents claim in January a scan revealed there was no evidence of the disease, but the tumour reappeared in an April scan.

A Go Fund Me page that was set up for the family has raised over $65,000 and can be reached here.