Search for father with three kids who fled Sydney crash

A search is under way for a father who pulled his children from a vehicle and fled a collision at Menai in Sydney's south.

Witnesses raced to the rescue of a woman stuck in one car before emergency services took over.

Plenty in the street heard the bang as a Mitsubishi ute flipped on its side after hitting a Mazda Sedan.

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In a matter of seconds a door opened on the ute and the father and his three children climbed out.

Vahid Tabakol said he saw them walk off.

"As I was walking towards it i see a man and three younger children walking away," he said.

Neighbours rushed to help the 43-year-old driver of the Mazda.

It was left to residents to stay by the driver's side until paramedics arrived.

"We saw the woman, she was crying and screaming and then the guy just kind of ran off with his kids," Joy Zaher said.

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Tabakol said he and other residents were worried the children might have suffered concussion and needed medical attention.

Police are continuing to search for the father.

The Mazda driver suffered only minor injuries.