'The children are about to go back to school like thousands of others in Austria,' sad the head of the family's security, at the Amstetten-Mauer psychiatric clinic where they are being cared for.

He added that the children would receive extra protection to stop them being harassed by paparazzi photographers, according to a report in the daily Kurier newspaper.

The two boys and one girl, aged 12, 14 and 15, were adopted and brought up by their father Joseph Fritzl, 73, and his wife Rosemarie, 69.

Fritzl told his wife that their daughter Elizabeth had left the three with him as babies saying she could not look after them.

The trio went to school as normal, apparently unaware that their mother and three other siblings, aged five, 18 and 19, were imprisoned in a bunker under the family home at Amstetten, some 100 km west of Vienna.

It was not known where the children would resume their education, but officials at their former schools indicated that they were preparing to welcome them back.

Only weeks after being admitted to the psychriatric clinic, the three children said they missed their classmates and wanted to return to school.

Maria Hosa, headteacher of a private school in Amstetten, told Kurier that the 15-year-old daughter returned to her school in June and finished the academic year with good results.

Two of the children, a girl of 19, and a boy of 18, who lived their whole life underground without ever having seen daylight are receiving private tuition, the family's lawyer, Christoph Herbst, said.

Elisabeth Fritzl, 42, bore seven children, including one who died, with her father during 24-years of sexual abuse in a windowless bunker beneath the family home.

Fritzl is expected to be charged at the end of September. -- AFP