A young girl is fighting for her life after being hit by a ute outside a primary school in north-western Sydney.

Shortly before 4pm today, police were called to Clower Avenue in Rouse Hill, where they were told a five-year-old girl had been riding a scooter on a footpath when she was struck by a ute.

Ambulance paramedics treated her at the scene before taking her to Westmead Children's Hospital.

According to police, the girl's condition is critical.

Clower Avenue is around 40km north-west of the Sydney CBD, and is home to Rouse Hill Public School.

The driver of the ute, a 43-year-old man, has been taken to Westmead Hospital for mandatory testing.

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