Detectives believe that at least three more women could have been killed by sadistic John Sweeney who was today convicted of murdering two former girlfriends.
Carpenter Sweeney cut up the bodies of Melissa Halstead and Paula Fields and threw the bits in canals in England and Holland.
Now police in both countries fear other former lovers met the same fate.
Sweeney also launched an axe attack at girlfriend nurse Delia Balmer who was only saved when a neighbour arrived to help.
He would boast of his woman-hating attacks in paintings and verse he wrote, the Old Bailey heard.
In one picture showing a bloody axe, he called himself the Scalp Hunter. In a poem he said he had fed Miss Halstead to the fish.
Some 300 paintings, wooden sculptures and poems were found at his home when he was arrested while on the run in 2001.
And similar works were found in his prison cell at Gartree Prison when he was arrested for murder last year.
Police found many clues to his twisted mind and murderous attacks in the works.
Liverpool-born Sweeney, 54, was found guilty of murdering Miss Halstead and Miss Fields, and perverting justice.
He will be sentenced tomorrow after refusing to leave the cells today.
The judge, Mr Justice Saunders, said he would give Sweeney a last chance to change his mind and go into the dock to be sentenced.
Brian Altman QC, prosecuting, asked the judge to impose a whole life term on the life sentences he faces so he would never be released.
Sweeney is already serving four life terms imposed in 2002 for the attempted murder in 1994 of Miss Balmer and having four guns when he was arrested while on the run.
Miss Balmer said he kept her prisoner in her flat and left her scarred for life after she received life-threatening injuries.
She said: "He had the axe above his head ready to finish me off. Then the man next door came out and risked his life. I had just curled up ready to go."
Former model Miss Halstead, 33, from the US, was killed in 1990. Her dismembered body was thrown into a canal in Rotterdam in the Netherlands.
She was only identified 18 years later by DNA, although her head and hands have never been found.
She had started a relationship with Sweeney who followed her to Vienna where he attacked her, and then to Holland where he killed her.
Her sister, Chance O'Hara, said: "She told me, if she ever went missing, that John Sweeney would have killed her. He had threatened that he would kill her and he would make sure no-one would ever find her body."
Sweeney wrote on the back of a scratchcard: "Poor old Melissa, chopped her up in bits, food to feed the fish, Amsterdam was the pits."
The body parts of Paula Fields, 31, were found in six holdalls floating in the Regent's Canal in Camden, north London, in February 2001. Her head, hands and feet are still missing.
The Liverpool-born young mother had arrived in London 14 months before and fell into prostitution to support a drug habit.
She was last seen at Sweeney's north London flat a few weeks before her death.
Her sister Irene Allahgreen told the court in a statement that the months before her death were only a small part of a "normal life".
She added: "We hope to God John Sweeney will never be released."
Mr Altman told the jury: "Police discovered amongst his possessions often lurid and demonic sketches and paintings, as well as pages of verse which reveal an obsessive and virulent hatred of women, and a preoccupation with dismemberment.
"By butchering and disposing of bodies in this way, the killer had intended that neither they should be identified, or he should be."
Now detectives want to know what happened to three other former girlfriends who have not been seen for many years.
A trainee nurse called Sue from Derbyshire was said to have gone to Switzerland in the late 1970s or early 1980s.
And they are also trying to trace two South American former girlfriends of Sweeney who have not been seen since the late 1990s.
Little is known about them, except that one was a Brazilian woman known as Irani, the other a Colombian called Maria.
Dutch police are also looking into Sweeney's claims to Miss Balmer that he killed two German men whom he caught with Miss Halstead.
The investigation into the murders is the first joint Anglo-Dutch investigation to be funded by Eurojust.
Asked if the three women were thought to have been murdered, Detective Chief Inspector Howard Groves said outside court: "We have some information which would suggest that is a possibility."
He said there was in particular information in relation to the Brazilian woman but would not comment further on what it was.
Mr Groves added: "Melissa Halstead and Paula Fields were killed and their bodies disposed of in the most callous and undignified manner possible.
"Sweeney had finally convinced himself that he would never be caught for these heinous crimes.
"As he contemplates a life behind bars, I can assure him that this investigation will continue as we seek to identify and trace other potential victims."