Eleven others have been injured and were taken to hospitals by helicopter and road.

A further 18 passengers were unhurt in the incident which happened just after 11.30pm (local time) on Sunday in the town of Greta in New South Wales.

Police said emergency services were called to a roundabout as they responded to reports that a "coach had rolled".

The bus driver, a 58-year-old man, was taken to hospital under police guard for mandatory testing and assessment, according to officers.

A police statement said: "A crime scene has been established, which will be examined by specialist forensic police and the crash investigation unit.

"An investigation into the circumstances surrounding the crash has commenced."