Police have released an e-fit of a man who has raped three women and killed his last victim as they race to find him before he strikes again.

An unprecedented DNA sweep of 9,000 homes has been undertaken by detectives to catch the dark haired man who always strikes towards the end of the month.

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.

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

The rapist has attacked at least three women in three months, dumping his last victim’s body in a children’s playground.

Detectives are also using FBI techniques including offender and geographical profiling to narrow down the area in which 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.

The e-fit, shows a suspect who is described as being of Asian appearance, or with dark skin, and is aged between 30 and 45 years. It will feature on BBC's Crimewatch tonight.

Detective Inspector Vic Rae, of the Metropolitan Police homicide and serious crime command, said: "The e-fit and tonight's appeal on Crimewatch is designed to urge anyone with any concerns or suspicions to come forward.

“Someone has a brother or a son who may have acted suspiciously or been in the Queens Road area at the times of these attacks. It is vital they think of the community and come forward. This man must not be allowed to strike again."

All men who fit the description are being asked to give a mouth swab voluntarily. Those who refuse face further investigation.

The attacker’s DNA was not linked to the first two rapes until the murder but he does not match any known criminal 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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