Jailed French serial killer Michel Fourniret, who murdered at least eight girls or young women between 1987 and 2001, has died aged 79, officials say.
Fourniret died in the secure unit of a hospital in Paris, the public prosecutor said on Monday.
Dubbed the "Ogre of the Ardennes", he was serving two life sentences for the kidnappings and killings.
Fourniret's wife, Monique Olivier, was also given a life sentence for complicity.
Fourniret was jailed for life in 2008 after being convicted of the murders of seven girls and young women. In 2018 he was given a second life sentence for the killing of a mobster's companion.
He also confessed to several other murders, including that of British student Joanna Parrish.
Fourniret's victims - most of whom were raped - were aged between 12 and 30. They were shot, strangled or stabbed to death.
Most were killed in the Ardennes region of northern France and in Belgium.
Paris prosecutor Remy Heitz said Fourniret had died at La Pitié Salpêtrière hospital where he had been admitted on 28 April from the nearby Fresnes prison.
Le Parisien newspaper said Fourniret had been suffering from a heart condition and Alzheimer's, and that doctors had placed him in an artificial coma. Mr Heitz said an investigation into his death had been opened.
Fourniret was first convicted of a sexual crime at the age of 25 when he received an eight-month suspended sentence for attacking a girl in his native Ardennes.
In 1984 he was jailed for attacking another young woman and it was during his time in prison that he began a correspondence with Olivier.
According to prosecutors, she agreed to help him find young female victims if, in return, he killed her husband. On his release from prison in 1987 she was waiting outside and they committed their first crime together barely two months later.
Who were Fourniret's victims?
In December 1987, Monique Olivier pulled up to 17-year-old Isabelle Laville when she was walking home from school in Auxerre.
She told her she was lost, and convinced her to get into the van to help her with directions. As they were driving, they stopped to pick up Fourniret. They said that his car had broken down.
The truth was that the couple had been watching Isabelle for a while, and had specifically targeted her that day. Once the three of them were in the van together, Fourniret raped and murdered Isabelle.
Isabelle was their first victim, but over the next 16 years the couple collaborated in the abduction and murder of at least eight girls and young women in France and Belgium.
They were finally stopped in 2003, when a 13-year-old girl Fourniret was trying to kidnap managed to escape, leading to his and Olivier's arrest.
Fourniret's known victims are Isabelle Laville, Fabienne Leroy, Jeanne-Marie Desramault, Elisabeth Brichet, Natacha Danais, Celine Saison, Mananya Thumphong, Farida Hammiche, Marie-Angèle Domèce, Joanna Parrish and Estelle Mouzin.
He was convicted of seven of these killings in the 2008 trial, and in 2018 was also found guilty of murdering Farida Hammiche, companion of a bank robber Fourniret had met in prison.
Later in 2018, he confessed to the murders of Ms Domèce, a disabled woman from Auxerre, and Ms Parrish.
His youngest victim, Estelle, was just nine years old when he murdered her in 2003. Her killing was unsolved until Fourniret eventually confessed in March of last year.