Detectives in Colchester are urging anyone who was in the Culver Square area of the town at 11am on Thursday, February 5 to get in touch after three attempted robberies were reported.
The first happened in Culver Square, with two further attempts in Eld Lane.
The first incident happened when a 34-year-old woman, of Colchester, was threatened by a man who demanded she hand over her money and possessions.
She refused and the suspect showed her a knife which was tucked in the waistband of his jeans. She still refused and the suspect walked away.
The next two offences happened in Eld Lane just minutes later. The suspect threatened a 52-year-old woman in the same way, but she refused to hand over anything and he walked away.
The suspect tried again with a 43-year-old Colchester man, also in Eld Lane. But again, nothing was taken from him.
Tim Harris, investigating officer, said: "Although this man was unsuccessful in all three of these attempts, his behaviour left all of his victims shaken and I want to arrest him before he tries again or escalates his behaviour.
"No-one in Colchester should have to put up with this sort of behaviour and I need people to tell me if they saw this man in the town that day, witnessed any of these incidents or have any other information which could help me to identify him.
"It is also possible that there may be other victims out there, including an elderly couple, who have not yet spoken to us and I would ask them to come forward so we can catch this man."
The suspect is described as a white man with a hooked nose. He was wearing a black baseball cap, black jacket, dark blue jeans and Nike Air Max trainers.
Anyone with any information is asked to contact Dc Harris at Colchester CID on 101 or call Crimestoppers, anonymously, on 0800 555 111.
