Fritzl appeared in court to be remanded in custody while doctors shielded the Elisabeth Fritzl and her six surviving children in isolation from a world they barely know.

'The DNA tests provided decisive evidence that the six children that Elisabeth gave birth to have the same father,' chief investigator Franz Polzer told a press conference.

'We're talking about Josef Fritzl, 73,' he added.

Elisabeth Fritzl, now 42, and her children, are sequestered 'in a treatment container that can be locked from the inside' to shield them from the outside world, child and youth pyschologist Paulus Hochgatterer told Austrian television.

One of the seven children she bore during her 24 years in captivity died shortly after birth. Three of the surviving children had never left the three cramped underground rooms where they were held and had never seen natural daylight.

Three other children were legally adopted by Josef Fritzl and lived with him and his wife Rosemarie upstairs in the family home, totally unaware of the fate of their siblings imprisoned in the cellar below.

The women and all the children face several weeks of treatment, Hans-Heinz Lenze, head of social services in Amstetten, told a news conference.

Psychologists were also available to Elisabeth's adult brothers and sisters, as well as the classmates of the three children allowed to lead 'normal lives', Mr Lenze said.

'Only very gradually are they being exposed to the outside world,' he said, adding that 'given the circumstances, they're actually doing quite well.'

The two sets of children, who had been completely unaware of each others' existence, were tentatively beginning to get to know one another, even if two of the three who had spent all their lives underground 'have a way of communicating that is anything but normal', said Berthold Kepplinger, director of the psychiatric clinic in Amstetten-Mauer.

Austrian Justice Minister Maria Berger warned media that they could be fined up to 20,000 euros (S$42,000) for publishing photos of the victims or details of their private lives where there was no express need.

'It's important that the victims are now left in peace,' Judge Berger told a news conference in Vienna.

Remanded in custody
The father was remanded in custody when he made a first appearance before a judge on Tuesday. Fritzl has also expressed his regret to the town chief in Amstetten.

'He looked at me with a face full of remorse and said: 'I'm very sorry. I regret this very much for my family,' said Mr Lenze, municipal chief of Amstetten and head of its social services, who met Fritzl while he was in police custody at the weekend.

He now faces 15 years in jail if convicted of rape and sequestration.

Doctors would determine when police would be allowed to question Elisabeth Fritzl and the children, but that was unlikely to be for several days, Mr Lenze said.

Authorities were looking for a special school for the children and they have proposed changing the names of Elisabeth, her children and her adult brothers and sisters, Mr Lenze said. -- AFP