Girl, 2, dies in hospital after assault in Guildford West

A toddler has died in hospital from injuries she suffered when she allegedly was bashed at a home in Sydney's west this week, police say.

An assault charge against 23-year-old Mohammed Khazma is expected to be upgraded to murder after the two-year-old girl died in The Children's Hospital at Westmead late on Tuesday night.

Charges are expected to be upgraded against Mohammed Khazma over the alleged bashing. Photo: Facebook

Police allege Mr Khazma physically assaulted the little girl on Monday afternoon in a granny flat in Marian Street, Guildford, where he lived with the girl and her mother.

The relationship between Mr Khazma, who had allegedly only met the girl's mother a few weeks ago, and the toddler cannot be detailed for legal reasons.

It's understood the mother was present when Mr Khazma allegedly physically assaulted the child. She was able to intervene and leave the granny flat with her daughter in her car.

The mother drove to a relative's home in McCredie Road in Guildford West, where neighbours reported hearing a woman screaming "You have killed my baby!".

Officers who were first on the scene just before 3.30pm discovered the girl unconscious and not breathing in the car. They performed CPR until paramedics arrived and took the girl to hospital in a critical condition.

Mr Khazma was arrested at a nearby park about 5pm on Monday.

Mohammed Khazma, charged with bashing a baby in Guildford. Photo: Facebook

"It's shocking," said Rosehill Local Area Commander, Acting Superintendent Glen Parks. "It's shocking for the community, it's shocking for the police attending ... It's difficult to comprehend."

Police set up crime scenes at the house on McCredie Road and the granny flat on nearby Marian Street in Guildford.

Mr Khazma originally was charged with reckless assault causing grievous bodily harm, and he did not apply for bail when his case was mentioned in Parramatta Local Court on Tuesday.

A NSW Police spokeswoman said the man's charges were expected to be upgraded to murder at his next court appearance on January 12.