By his own confession, Austrian police say, Josef Fritzl held his daughter inside a hidden, windowless cellar for nearly a quarter of a century, raping her repeatedly and forcing her to give birth to seven of his children.

When two of the children were freed this week, authorities said they were seeing sunlight for the first time.

Police say Fritzl, a 73-year-old electrician, confessed Monday to imprisoning his daughter Elisabeth, and to incest, in a case that has horrified Austria and unleashed questions about how such a crime could take place, apparently undetected, for such a long time.

"We are being confronted with an unfathomable crime . . . an incomprehensible brutality," Interior Minister Guen- ther Platter said.

The case bears grisly resemblance to another headline-grabbing incident in which a 10-year-old Austrian girl named Natascha Kampusch was kidnapped on her way to school in 1998 and trapped by a sexual predator for eight years inside a tiny dungeon in a Viennese suburb before finally escaping.

If Austrians were shocked enough by Natascha's ordeal, the allegations surrounding the Fritzl family have left them positively dumbfounded. Especially disturbing is that, with the Fritzls, the alleged crimes were all within a family.

Elisabeth Fritzl, now 42, told authorities that her father drugged and handcuffed her in 1984 after luring her to the basement of their rambling home in Amstetten, an industrial town 75 miles west of Vienna. He later told his wife, Rosemarie, who is Elisabeth's mother, and anyone else who asked that his daughter had run away.

Instead, he kept her locked in a 540-square-foot warren of underground rooms, some barely large enough to stand upright in, authorities say. The door to the prison was concealed behind shelves and secured with an electronic lock to which only Fritzl had the code.

While in captivity, Elisabeth Fritzl gave birth to the seven children, police say, based on information from her and her father. One died soon after birth, police say, and the father disposed of the body in the incinerator. Over the years, Fritzl took three of the children upstairs to the main part of the house, telling his wife that they were the missing Elisabeth's children whom she had sent back to be cared for. Rosemarie Fritzl, police say, either believed her husband's account, or did not dare to challenge it.

Three other children, today ages 5, 18 and 19, were confined with Elisabeth Fritzl in the dungeon. It is unclear why Fritzl chose to imprison some and raise others in more normal conditions.

Josef and Rosemarie Fritzl, 69, had seven children.

"This man, who already had a family with seven children by his wife, had in this cellar seven more children by his own daughter," Franz Polzer, head of the Lower Austrian Bureau of Criminal Affairs, said Monday at a crowded news conference. Polzer described Fritzl as an "authoritarian."

The deception unraveled when Elisabeth Fritzl's 19-year-old daughter became gravely ill and had to be taken to a hospital.Details of her illness were not revealed, but police were called when medical authorities became suspicious. After his arrest, the father eventually revealed the existence of the basement prison. Police on Sunday freed Elisabeth Fritzl and the two other children, all of whom were quickly put in the care of medical and mental health experts.

DNA tests were being conducted to verify that Fritzl had fathered the children. Elisabeth Fritzl, as she was being taken away, looked wan and far older than her age.

Neighbors in the town of 22,000 inhabitants expressed disbelief at the stunning string of revelations. Several, speaking to reporters, described the Fritzls as a seemingly normal family; they often saw Rosemarie Fritzl shopping at the local bakery and grocers.

Alfred Dubanovsky, a neighbor who rented a small flat over the secret cellar, told the Kurier newspaper that his suspicions were never aroused -- although he occasionally heard inexplicable knocking from the basement and saw Fritzl taking food in that direction.

"I cannot imagine that nobody noticed anything," Ingeborg Pucher-Matzner, a psychologist, told the Austrian news agency APA. She said that within the family, it was likely "that there was a climate of enormous psychological and physical violence, [and] that in a situation like that nobody is asking questions because one is afraid of the consequences."

Austrian psychologist Reinhard Haller said in a television discussion Monday that the case was especially haunting because it happened "among us, in the middle of town."