The murder of the 13-year-old Surrey girl Milly Dowler is being investigated for possible links with two other killings and at least four assaults, police say.
Officers from Surrey Police are liaising with Scotland Yard detectives investigating the murders of the French student Amelie Delagrange and the teenager Marsha McDonnell.
The Metropolitan Police homicide team has already linked the two London murders and believe the killer is responsible for a series of attacks throughout the capital during the past two-and-a-half years. Most of the victims have been young blonde women who have been attacked from behind.
A senior Metropolitan Police officer, commenting on the three murder inquiries, said: "We are liaising about possible links."
Officers investigating the abduction of Milly, who was snatched on 21 March 2002 as she walked to her home in Walton-on-Thames, announced details yesterday of a potential breakthrough. It centres on a red car seen yards from where Milly was last seen leaving the town's railway station. Police believe the Daewoo Nexia may have been used in the abduction of the teenager, whose body was found buried in a wood in Hampshire six months after she disappeared. They suspect the car may have been driven by someone with connections with Walton-on-Thames at the time of the murder.
The 1996 N-registration vehicle was filmed at 4.33pm, 25 minutes after Milly was last seen. The car appeared to be sitting low on its rear wheels.
The inquiry is the largest homicide investigation undertaken by Surrey Police and is one of Britain's most high-profile unsolved murders. The force has followed up more than 11,500 lines of inquiry, taken more than 4,200 statements and received more than 6,000 phone messages in the course of the inquiry, codenamed Operation Ruby.
It has also been investigating the movements of Lance Corporal David Atkinson, 31, the soldier who murdered Sally Geeson, a Cambridge student, at New Year and then jumped to his death from the window of a hotel in Glasgow. Initial findings suggest, however, that the soldier was on a military course at the time of the abduction. The force said it was also investigating a registered sex offender who lives in south-west London in connection with Milly's abduction and murder.
Detective Chief Inspector Brian Marjoram, who is leading the search for Milly's murderer, said: "We remain determined to find the person responsible. Whoever that is should be looking over their shoulder."
Surrey Police stressed yesterday there was as yet no formal link between its hunt for Milly's killer and the Scotland Yard investigation into the murder of Ms Delagrange and five other linked attacks, codenamed Operation Yeaddiss. Det Chief Insp Marjoram, said: "We are liaising closely and we will keep an open mind, although the offences are not formally linked."
Police have already linked a series of attacks in south-west London, including the murder of Ms Delagrange, 22, a French student bludgeoned to death on Twickenham Green as she walked home after a night out in August last year. The killer is also thought to be responsible for the murder of Marsha McDonnell, 19, who was hit over the head yards from her front door in Hampton in February 2003.