Police are investigating two shop robberies on Sydney’s North Shore.

About 4.45pm on Saturday 4 May 2013, a man entered a boutique on Willoughby Road at Crows Nest.

He threatened the female employee and demanded money from the cash register.

The woman was unable to open the register and the man fled the premises without taking anything.

It is unknown whether he was carrying a weapon.

A short time later, a man entered a grocery store on the Pacific Highway, Crows Nest, and threatened the 29-year-old female employee and demanded cash.

He took cash from the register before fleeing the premises.

The man for both offences has been described as 40 years of age and 170cm tall. He was wearing black pants and a dark-coloured jacket.