Police probing the murder of a Muslim woman are investigating whether her killer also knifed to death a vulnerable man in a "frenzied" attack earlier this year.
Nahid Almanea, 31, was stabbed 16 times and left to die as she walked along a quiet footpath in Colchester, Essex, last Tuesday.
Her killing came just two months after James Attfield, 33, was stabbed 102 times on his arms, hands, back, neck and head in what police described as a "senseless and frenzied" attack in the town.
The two brutal knife murders have sparked fears that a serial attacker may be on the loose.
Essex Police said today that they are probing the possibility that the murders might be linked, but said there is no firm proof they are.
In a statement, D etective Chief Superintendent Steve Worron said: " We do not yet know whether the murders of Nahid Almanea and James Attfield have been committed by the same person or people.
"A criminal profiler from the National Crime Agency has carried out a thorough assessment of all the evidence in connection with both murders.
"A decision has been taken that they remain separate but parallel investigations at this time.
"However the circumstances of both crimes mean that we must consider the possibility that the same killer or killers are responsible.
"We are continuing to explore this line of inquiry, along with many others, and both investigations are being continually resourced and are receiving equal precedence."
He said the two murder inquiries would be working closely together and any evidence uncovered in either murder hunt will be looked at by officers on both teams.
Ms Almanea, who was originally from Saudi Arabia but studying English language at Essex University, was wearing a full-length robe called an abaya and a hijab headscarf when she was attacked while walking along the Salary Brook Trail at around 10.40am on Tuesday morning.
Detectives had earlier said they were looking into the possibility that she was targeted because of her Muslim dress.
And they are appealing for help tracing two men spotted near the murder scene.
The first man is described as white, aged between 18 and 25, of medium build and with dark hair, was seen running up Hewes Close at around 10.56am on the day Ms Almanea was murdered.
He was wearing a long-sleeved, plain red hooded top and dark trousers.
Police are also appealing for help to track down a man who tried to attack a jogger less than a mile from where Ms Almanea was killed.
The white man, thought to be in his early 20s, around 5ft 7in and of medium build with a narrow face and possibly fair hair, tried to attack the woman in Peache Road, Colchester, at around 10pm.
Officers said the attack's location and reports that he had a knife mean this suspect is also of interest to the Almanea murder investigation.
Police have received more than 100 calls from members of the public with information in the wake of last week's murder, but urged more people to come forward.
Mr Worron said: "I still firmly believe that the answer to these investigations will come from within the Colchester community.
"We continue to gather all available forensic evidence and this will undoubtedly open up new lines of inquiry.
"But what I really need is to hear from anyone in the community who has any suspicions about who may have committed these dreadful crimes."
A 19-year-old man arrested in connection with Ms Almanea's murder was released this morning.
Essex Police have been scouring hedgerows and searching a pond near the murder scene in the hunt for clues, and have drafted in help with the murder inquiries from the Metropolitan Police.
Meanwhile, additional police patrols have been laid on across Colchester as officers urged locals to remain vigilant.
Superintendent Steve Ditchburn said: " Our advice to people is that we have now had two knife murders in Colchester in less than three months where the motive for the attacks remains unknown. Against that background we would advise everyone in the town to remain vigilant.
"Both of these attacks were on lone people who were in locations where it appears no-one else was nearby at the time.
"For that reason we would remind people to take sensible precautions to stay safe. This includes avoiding any situations in which you could find yourself isolated and alone in a public area."
He added: " And we would ask families, friends and neighbours to keep an eye out for each other and provide support to anyone they consider vulnerable."
Anyone with information about the murders should to contact the Major Investigation Team on 01245 282103, Essex Police on 101 or contact Crimestoppers, anonymously, on 0800 555 111.