The location of the attacks are marked above. The area highlighted in blue is where police are targeting their DNA sweep

A DNA sweep of residents in 9,000 homes has been launched in a race to catch a murderer and serial rapist who strikes towards the end of each month.

Murder squad detectives have been drafted in from all over London to help to complete the canvassing of houses within a ½-mile radius in Walthamstow, East London.

The rapist has attacked at least three women in three months, murdering the latest and leaving her body in a playground.

It will take at least a month to take a swab from every male matching the attacker’s description, and detectives fear that another woman will be attacked within days. All men who fit the description are being asked to give a mouth swab voluntarily. Those who refuse face further investigation.

Detective Superintendent Vic Rae, of the Metropolitan Police homicide and serious crime command, said: “This guy has attacked three women in three months and we have got to do everything within our powers to apprehend him before he strikes again. Our concern is that he will strike before the end of the month.”

Detectives are using FBI techniques including offender profiling and geographical profiling to narrow down the area where the killer could live, based on the attack locations.

His first victim, 59, was attacked in her own home in Queen’s Road on March 24 after he began speaking to her as she reached her house at 1am. He pushed her inside and beat her before raping her.

On April 22 at 1am he approached a 46-year-old woman as she walked home in Selborne Road, asked for directions and then dragged her into an alley where he attacked her.

His third victim, Michelle Samaraweera, 35, was last seen on May 30 at 1.15am when CCTV captured her leaving a supermarket with two bags of shopping.

Her body was found in a small park, also in Queen’s Road, at 5am with her shopping nearby.

Several people have told police that they were in the park at 3am and did not see her body so police are appealing for help in tracing where she went for those missing hours. One possibility is that the murderer took her to a house before strangling her and then dumping the body.

Ms Samaraweera’s sister, Ann Chanradasa, appealed yesterday for the killer to give himself up. She said: “He’s a sick, sick man who obviously needs help.”

The attacker’s two surviving victims described him as dark-skinned, aged 30 to 36 and about 5ft 8in to 5ft 10in tall, speaking with an accent.

His DNA was not linked to the first two rapes until the murder but he does not match any profile on the national database. One theory is that he is a new arrival to Britain who has struck abroad before.

Officers are also ploughing through hundreds of unsolved sex assaults in the Walthamstow area. Police carrying out the door-to-door sweep, known as Operation Eklutna, accept that the killer may no longer live in the area or may just work there.

Mr Rae, leading the operation, said: “I don’t know of any other inquiry that has done DNA on this scale door-to-door before. I have grave concerns that he will strike again.”

Women in the area have been warned by police to be extra vigilant and not to walk alone at night.

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