Woman assaulted after getting off train

An 18-year-old woman has been indecently assaulted near a train station on Sydney's affluent north shore in the early hours of Sunday.

The woman was crossing Lindfield Avenue after getting off a train at Lindfield Railway Station at about 1.45am when she was attacked from behind and indecently assaulted.

When another man came to the woman's rescue, her attacker fled north along Lindfield Avenue.

Police said the man is described as being of Asian appearance, about 20-years-old, approximately 175cm tall, with black hair, black stubble and a stocky build.

He was wearing a grey hooded top and dark-coloured pants.

Police are urging anyone with information to call Crime Stoppers on 1800 333 000.