A 73-year-old Austrian electrical engineer has confessed to holding his daughter captive in a secret, windowless cellar for 24 years and fathering seven children by her, police said yesterday.

The case, centred on a nondescript two-storey building in the small industrial town of Amstetten, bears chilling similarities to that of Austrian Natascha Kampusch who spent eight years locked up in a basement before escaping in 2006.

Some parts of the cell in which the family were kept were no more than 1.70 metres high and officials said the basement even contained a padded cell.

"This is an appalling crime. I know of no comparable case in Austria," Franz Prucher, head of security for Lower Austria, told a news conference.

Elisabeth Fritzl, 42, says her father, Josef Fritzl, lured her into the basement of the block in 1984 and drugged and handcuffed her before imprisoning her.

Three of her children, aged 19, 18 and 5, had been locked up in the basement with her since birth and had never seen sunlight, police said, raising worries about their physical and mental state. The younger two were boys, the eldest a girl.

Three other children - two girls and one boy - were brought up by Josef and his wife.

As well as confessing to locking up his daughter for 24 years and siring the seven children, Mr Fritzl also admitted to burning the body of the seventh child in the heating system when it died soon after birth, said Mr Polzer.

All the victims are receiving medical treatment, said police. State prosecutors said Mr Fritzl would be summoned before a judge.

Investigators spent the day combing through the cells where the victims had been held captive. Forensic experts in white uniforms and gloves carried out boxes of evidence from the house which is on a busy street with shops.

Mr Fritzl had hidden the entrance to the cell behind shelves and only he knew the secret code for the reinforced concrete door, said officials.

Photographs showed a narrow passageway leading into other rooms which included a cooking area, sleeping area and a small bathroom with a shower. A tube provided ventilation.

Amstetten, located in rolling hills about 130 km west of Vienna, is an industrial town of about 22,000 people.

The case unfolded when the 19-year-old girl became seriously ill and was taken to hospital, prompting doctors to appeal for the girl's mother to come forward to provide more details about her medical history.

Mr Fritzl then brought Elisabeth and her remaining two children out of the basement, telling his wife - who thought their "missing" daughter had chosen to return home, police said.

Elisabeth agreed to make a comprehensive statement to the police after receiving assurances she would have no further contact with her father, who she said abused her from the age of 11.

Ms Kampusch, who spent her teenage years held captive, offered to help the victims and told ORF radio she might talk to the family.

"I can imagine that it is very difficult both for the mother of the children as well as for the wife of the perpetrator to get through this," she said.

Psychiatrist Max Friedrich, who treated Ms Kampusch, said the children were undergoing tests in hospital, in particular for problems with their eyes and skin due to the lack of daylight.

"And socially... the (children) could not develop any sort of sense of community which they would get from going to school or playgroup," Mr Friedrich said.