Four people have been hospitalised after a car carrying three young children slammed into a tree in northwest Sydney.

Emergency crews were called to Putty Rd at Colo Heights about 10.15am on Saturday following reports of the crash.

WATCH THE VIDEO ABOVE: Seven-year-old airlifted after Colo Heights crash

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Footage from the scene shows the bonnet crumpled and the front of the Toyota Kluger heavily damaged.

Paramedics assessed the five occupants — two adults and three children aged four, seven and eight — at the scene.

Paramedics assessed five occupants at the scene. Credit: 7NEWS

The seven-year-old boy was airlifted to The Children’s Hospital at Westmead with a shoulder injury in a stable condition.

The four-year-old boy was taken by road to the same hospital with a head injury, also in a stable condition.

The eight-year-old child did not require further treatment.

The 35-year-old female driver was treated for minor chest and abdominal injuries before being taken to Westmead Hospital in a stable condition.

The 40-year-old male front passenger was treated for back injuries before being transported to Westmead Hospital in a stable condition.

An investigation into the crash is underway.