Josef Fritzl today claimed that he had been abused as a child, as the retired electrical engineer went on trial for imprisoning his daughter in the cellar as a sex slave for 24 years.

The 73-year-old admitted rape, incest and false imprisonment, but denied enslaving Elisabeth, 18, in the soundproofed basement of his home as the rest of his family remained oblivious upstairs.

He also denied murdering one of the seven children he fathered with Elisabeth in the cellar.

"I had a very difficult childhood," Fritzl said in a trembling voice at his trial in St Pölten, Austria.

"My mother didn’t want me. She was 42 when she had me. She simply didn’t want a child and she treated me correspondingly. I was beaten."

Earlier Fritzl held a blue lever-arch file containing his court notes in front of his face, hiding his features in defiance or shame, as he shuffled into the courtroom escorted by police.

Mr Fritzl is accused of imprisoning his daughter in the windowless cellar where no natural light penetrated, raping her on average three times a week, fathering seven children by her and allowing one of them to die by failing to seek medical treatment when it suffered breathing difficulties at three days old.

Most of the trial is taking place behind closed doors. Media and public were admitted for the opening statements this morning, but then excluded.

This afternoon the court was said to have begun watching an 11-hour video testimony in which Elisabeth recounted her ordeal.

The tape was recorded last July so she would not have to see her father in court. The video was stopped at points for Fritzl to respond, said Franz Cutka, a court spokesman. The court will continue to watch it tomorrow.

Neither Mr Fritzl's wife, Rosemarie, nor any of his other children will give evidence at the trial because they have refused to do so.

Four expert witnesses are ready to give evidence if necessary: a doctor who specialises in newborns, a psychiatrist, and an electrical engineer and a surveyor who inspected the dungeon.

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