NSW toddler dies after 'running onto road'

A toddler has been fatally struck by a car after he slipped from his grandmother's grasp and ran onto a western Sydney road, witnesses say.

The young boy, believed to be aged 18 months, was struck on Marion Street at Auburn shortly before 9.30am on Thursday.

Nearby residents raced to the scene, including a student nurse who says she dodged traffic to get to the boy and his grandmother.

"I got to the lady and she was screaming with baby in her (arms) held tight to her chest," Mariam Zreika, 19, told News Corp.

"I checked the pulse rate, no pulse ... so I put him on the side. As I did that he took a couple of breaths inside and out.

"Then police arrived and immediately started resuscitation, then they told me to move away."

The toddler's parents arrived within minutes of the accident.

Witnesses told the Seven Network the driver tried to avoid the boy and the car ended up hitting a brick wall.

He was taken to Westmead Children's Hospital but died a short time later, police say.

His grandmother wasn't injured but was treated for shock while the car driver, reportedly a P-plater, was taken to Auburn Hospital for mandatory testing.