A young girl is about to undergo surgery after her leg was broken when a man riding an electric scooter allegedly crashed into her in NSW's hunter region.

Police were told the man lost control and crashed into a four-year-old girl, breaking her leg, at a shopping centre on Main Road in Cardiff about 10am today.

He allegedly did not stop to help the girl.

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"The man immediately retrieved his scooter and left the scene," NSW Police said in a statement.

Paramedics treated the girl, who also had a cut to her face, before taking her to John Hunter Hospital in a stable condition "where she is expected to undergo surgery".

"Police have released CCTV vision of a man who they believe may be able to assist with their inquiries," NSW Police said.

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"The man is described as being of Caucasian appearance, aged in his late 30s, with short brown hair, and has a large tattoo on his right forearm.

"He is depicted wearing a black hat, blue sunglasses, black shirt, black shorts, red belt, dirty white shoes, grey 'Nike' hooded jumper, black shorts, and red shoes, and was riding a black electric scooter."

Anyone with information is urged to contact Crime Stoppers.