German prosecutors on Friday formally closed a decades-long investigation into Aribert Heim, a Nazi-era doctor, who was one of the world's most wanted men for his sadistic killings of concentration camp victims during World War II.

A state court in the city of Baden-Baden concluded that Austrian-born Heim had indeed died of bowel cancer in 1992 in Cairo, as previously reported.

Nazi hunters had said at the time they were concerned that he might have faked his death to evade capture and fool journalists.

Heim, who practiced as a gynecologist in Germany after the war, fled to Egypt as investigators closed in and hid for 30 years under the assumed name Tarek Hussein Farid. German prosecutors checked documents and spoke to witnesses in Cairo before reaching their conclusion.

Heim was reputed to have conducted pseudo-experiments, killing patients by injecting poison or carrying out major surgery without anesthetic at Mauthausen concentration camp in Austria.

In a television documentary in 2009, his son spoke of his revulsion for his father, but admitted the family had remained in contact with him during his exile.