Sydney: A Christmas carols event descended into mayhem in Sydney after a fireworks display got out of control, injuring at least nine people including three children.

According to local media, emergency services were called to the event at Allambie Heights Oval in the Northern Beaches region of Sydney at around 9:30 pm on Sunday and were told upon arrival a firework had "shot into a crowd" during the event.

An 11-year-old boy was found to have sustained burns and a chest injury and was taken to the hospital. An eight-year-old girl and a 12-year-old boy were also hospitalized but have been released later.

Six other people were treated on the scene for minor injuries and left before paramedics and police arrived.

Police have established a crime scene at the oval. Inspectors from SafeWork New South Wales will attend the scene on Monday.

(With UNI inputs)