Colchester murders: Stabbing deaths 'could be linked'
Police have said they cannot rule out a possible link between two murders in an Essex town.
Officers from seven forces have been drafted in and extra patrols scheduled.
Det Ch Supt Steve Worron, from Essex Police, said: "We do not yet know whether [they]... have been committed by the same person or people".
He added the inquiries would remain separate but would run in "parallel".
Police from Bedfordshire, Cambridgeshire, Hertfordshire, Kent, Norfolk, Suffolk and the Met are now involved in the investigations.
Officers will patrol locations across Colchester that are similar to those where the murders were committed.
Det Ch Supt Steve Worron said: "We have over 100 detectives, close to 40 specialist search officers and hundreds of officers have been drafted in around reassurance patrols.
"We ask people to be vigilant, to take care of themselves and to look after each other as well.
"I'd ask people to think about their movements around open spaces and isolated areas."
Det Ch Supt Worron said 350 house-to-house inquiries had been carried out on Friday.
"We do not yet know whether the murders of Nahid Almanea and James Attfield have been committed by the same person or people," he said.
"There are significant similarities between both offences.
"Both were committed in open spaces that weren't widely used and both victims died as a result of knife attacks.
"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 criminal profiler has been brought in to check evidence from both murders.
He urged witnesses to come forward if they had seen a man running along Hewes Close at about 10:55 BST on the day Ms Almanea was murdered.
The man, described as white, aged between 18 and 25, with dark hair and wearing a red hooded top and dark trousers, was first spotted coming out of an alley near the Salary Brook Trail.
He also wanted to hear from anyone who had seen a man, described as white, in his early 20s, who looked unwell and was wearing a black hooded top, after a woman was attacked in Peache Road on 19 June.
Ms Almanea, 31, of Woodrow Way, was killed on a path near Avon Way as she walked to the University of Essex.
She was studying in Colchester as part of her PhD and had lived in England for less than a year.
Her body has been released by the coroner and was returned to her native Saudi Arabia earlier this week.
Police said father-of-five Mr Attfield, 33, died in a "frenzied" attack in Castle Park on 29 March.
He had wounds to his head, upper body and hands.
He had suffered a severe brain injury when he was hit by a car four years previously.