“He claims that he drank the blood of both women (and) that he ate parts of one of the women’s chest area,” prosecutor Christer Sammens told AFP.
“This has been corroborated by the coroner, who confirmed that there are bits of the body missing.”
The man, whose name was not disclosed, allegedly ate the body parts raw.
The two women, aged 18 and 32, had been placed as foster children in his parents’ home when they were younger.
He killed the 18-year-old woman in March 2005, stabbing her more than 40 times in her own home. Seven months later he stabbed the 32-year-old woman 60 times, also in her own home.
The motive for the killings was not known.
“He just says he has to murder people and drink their blood,” Sammens said.
The man was charged in a court in Gävle, in central Sweden, with two counts of murder on Thursday. Sammens said he expected the man to be sentenced to psychiatric care.