Woman assaulted in Sydney brothel robbery

A woman has been assaulted during a robbery by four masked men at a brothel in Sydney's inner west.

Police were called to the premises in Petersham just before 11.10pm on Thursday to be told the men had demanded money and assaulted the woman before leaving with a quantity of cash.

The 22-year-old woman was treated at the scene by ambulance paramedics.

A crime scene has been established and police are urging anyone with information on the robbery to call Crime Stoppers on 1800 333 000.