Almost 50 years after the ‘Boston Strangler’ murders prosecutors have said new DNA evidence linked a man, who confessed to the killings but was never convicted, to the last of the homicides.

“There was no forensic evidence to link Albert DeSalvo to Mary Sullivan's murder until today,” said Suffolk County District Attorney Daniel Conley at a news conference.

Prosecutors are warning however that the full string of murders might never be solved.

“These developments bear only on Mary Sullivan's murder. They don't apply to the other 10 homicides popularly attributed to the Boston Strangler,” said Mr Conley.

Even among experts and law enforcement officials there is disagreement to this day about whether they were committed by the same person.

The evidence came from DNA extracted from a water bottle that one of DeSalvo's nephews had drunk from.

It showed a strong family link to DNA recovered from the scene where Ms Sullivan was raped and killed in January 1964.

Based on that link, a judge authorised investigators to exhume DeSalvo's remains for final DNA testing,Mr Conley said.

He added that the body would be exhumed sometime this week and that the testing would be a quick process.

Eleven women were murdered in the greater Boston area from 1962 through 1964 in the Boston Strangler killings, after sexual assaults that took place in their homes.

The assaults, which targeted unmarried women, terrified the city.

DeSalvo, who was married with children, confessed to the murders, as well as two others, but was never convicted.

He was sentenced to life in prison for a series of armed robberies and sexual assaults and was stabbed to death in the state's maximum security prison in Walpole in 1973 - but not before he recanted his confession.

"The miracle of science and DNA evidence" has allowed investigators to identify her probable killer, police said in a statement.

Ms Sullivan is the only victim for which DNA evidence is available.