Just a short walk away from one of the Sydney’s most popular destinations — Manly Beach — a tourist has been brutally stabbed in the head by a group of teenagers.

The shocking street robbery, near Manly Wharf at Upper Gilbert Street yesterday evening, has left the 23-year-old hospitalised with serious injuries.

Police say he was walking up the stairs along the street, where he was threatened by three unknown boys aged in their late teens, before being stabbed with a knife to the head.

Officers have been told the teens threatened the man, demanding his wallet and mobile phone, before fleeing the scene empty-handed.

The teens were last seen running along Upper Gilbert Street, near Tower Street.

The injured man presented himself to Manly Hospital with a serious head injury. He will undergo surgery at a later date.