Doctors spoke today of the "astonishing" scene as the two groups of children born of Josef Fritzl's incest with the daughter were reunited at an Austrian hospital.

Three of the children, aged 19, 18, and five, were raised underground and never allowed to see daylight, while three other children were taken out of the cellar as babies and brought up by Mr Fritzl as his own grandchildren two floors above, in a well-kept villa in the town of Amstetten.

On Sunday, five of those children were reunited at a hospital near Amstetten along with the kidnapped daughter Elisabeth, now 42, and her mother, Rosemarie Fritzl. The sixth child, a 19-year-old girl, is in a critical condition on a life-support machine in a different hospital.

"It was astonishing how easy it was," said Dr Berthold Kepplinger, director of the clinic, who said that all the family members, including Elisabeth and her mother, had interacted very naturally.

Commentary: a society that nurtures secrets

What society would accept the probability of three children being left on the doorstep of Josef F and grant him adoption?

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• Pictures: house of horror

Background

• Why are child abuse scandals happening in Austria?

• Analysis: damage caused may never be healed

• Austria: sedate town is stunned by news

• Police search other Fritzl properties in Austria

Related Links

• Incest father has sex assault conviction

• Why are child abuse scandals happening in Austria?

• Pictures: House of horror

Multimedia

• Comment Central: what about the neighbours?

News of the family reunion came as DNA tests confirmed that Mr Fritzl was indeed the father of Elisabeth's six surviving children.

The tests were ordered at the weekend after the shocking case of kidnap and incestuous abuse came to light, although their result does not come as a surprise. Mr Fritzl had already confessed to having imprisoned his daughter, Elisabeth, for 24 years and to having fathered a total of seven children by her, including a boy who died shortly after birth.

"The DNA tests provided decisive evidence that the six children that Elisabeth gave birth to have the same father," Colonel Franz Polzer, the chief investigator, told a press conference. "We’re talking about Josef Fritzl, 73."

Colonel Polzer said that police had today inspected other properties owned by the retired electrical engineer to make sure that he was not holding other captives in similar underground cells. None were found.

Earlier today Mr Fritzl was remanded in custody for 14 days after appearing before a judge in St Poelten, the provincial capital of Lower Austria. He is not expected to be charged until the end of that period, but prosecutors said earlier that the charges could include "murder through lack of action" over the death of the baby boy, whose body he burnt in a domestic heating furnace.

Meanwhile, officials in Amstetten, the small town where the Fritzl family lived, said that Mr Fritzl's offspring - Elisabeth, her children and her own grown-up siblings - would be offered new lives and new names. "The name Fritzl has been muddied," said Hans-Heinz Lenze, head of the social services in the town.

Elisabeth Fritzl has told police that her father lured her into the cellar of their home in 1984, drugged and handcuffed her, and then kept her imprisoned.

The abuse came to light at the weekend when Mr Fritzl apparently allowed his 19-year-old daughter by Elizabeth out of the basement dungeon for treatment after she fell seriously ill. Doctors trying to explain her illness then issued an urgent appeal for her mother to come forward.

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