Three attempted robberies took place in Colchester town centre on Thursday.
They happened at around 11am. The first happened in Culver Square and the other two occurred in Eld Lane.
In the first incident, a 34-year-old woman from Colchester was threatened by a man who demanded she hand over her money and possessions.
She refused and the suspect showed her a knife that was tucked in the waistband of his jeans.
She still refused and the suspect walked away.
The next two offences happened in Eld Lane, minutes later.
The suspect threatened a 52-year-old woman from Colchester in the same way. She refused to hand over anything and he walked away.
The suspect then tried the same thing to a 43-year-old Colchester man, also in Eld Lane. Again, nothing was taken from him.
Police believe there may be more victims that may not have come forward and they would particularly like to speak to them, especially an elderly couple.
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 about the incidents is asked to contact Dc Tim Harris at Colchester CID on Essex Police 101.
People can also give information to Crimestoppers anonymously on 0800 555 111 or via an anonymous online form at www.crimestoppers-uk.org
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