Man stable after Sydney assault

A man has serious head and facial injuries after a suspected one-punch attack at Haymarket in central Sydney.

Police and paramedics were called to George Street about 12.45am on Sunday and found the injured man.

The man in his 30s was taken to St Vincent's Hospital in a critical condition and put in an induced coma but was later upgraded to a serious but stable condition and is in intensive care.

Police are investigating the attack as a potential one-punch assault and are reviewing CCTV footage.