A balaclava-wearing man brandishing a hypodermic syringe robbed a shop.
The man walked into West Hill Stores in Plynlimmon Road, Hastings, on May 31 brandishing a capped hypodermic needle.
He escaped with hundreds of pounds in cash and fled on foot towards Whitefriars Road.
The robber was white and slim and was wearing a black balaclava.
Detective Constable Dave Elcock said: "Thankfully the shop assistant was not hurt but she has been left very shaken by what happened to her.
"I need to speak to anyone who was in the area around the shop on Saturday morning and could have seen the robber outside the shop.
"We believe the man only pulled his balaclava on before he walked into the shop so people may have seen him acting suspiciously outside in the minutes beforehand.
"If you saw anything or know who was involved, please contact us."
Two men from Hastings aged 35 and 48 have been arrested on suspicion of robbery and questioned before being released on bail until 4 August.
Anyone with information should call 101 quoting serial 312 of 31/5, email email@example.com or call the independent charity Crimestoppers anonymously on 0800 555111.