A teenage boy has died after he slipped and fell into a lake in Sydney's south-west this afternoon.

New South Wales Police were called to Chipping Norton Lake, near McMillan Park, about 3pm today after being told a 14-year-old had gone missing.

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Divers and emergency services also attended after the boy failed to resurface.

A boy's body was retrieved from the water around 4.45pm following an extensive search.

It has since been formally identified as the missing 14-year-old boy.

A crime scene was established and police are conducting inquiries.