Shocking revelations from Josef Fritzl's daughter's dungeon diary tell of the anguish of her 24 years underground.

Less than a week before Fritzl, 74, stands trial on murder, slavery, rape and incest charges, extracts from his daughter's journal have been leaked to the media in Austria.

Elisabeth detailed how her father starved her and how he beat the six children he fathered with her.

On scraps of paper hidden in her prison, she wrote down the date and time of every slap, threat or beating dished out to her children by their father.

In one moving entry she records how she cradled her dying seventh child in her arms as he turned blue with breathing complications. "At least he's in a better world now," she wrote.

Fritzl burned the infant's body in an incinerator and scattered the ashes in the garden of the family home in Amstetten. It is this child's death that has led to the murder charge against him.

Elisabeth also records how she caught rats with her bare hands and how her children were fascinated by everyday objects such as a mirror or bathroom scales.

The youngsters would eat something and then stand on the scales to see if their weight had altered.

Another entry, dated March 2, 1991, records grimly: "Milk and other foodstuffs are almost all gone now."

She also details how Fritzl repeatedly raped and threatened her and how she tried to fight him off.

For five days, from next Monday, jurors in the small Austrian town of St Poelten will hear testimony so harrowing the judge has ordered they listen to no more than two hours of it a day.

The journal of Elisabeth's 8642 days underground explains how casually her six surviving children were split up so three would live upstairs with Fritzl and his wife while three stayed entombed with their mother.

One baby was taken upstairs only because a piece of thread was caught around his toes making him cry. An angry Fritzl feared the baby's howls would alert neighbours and took the infant upstairs to calm it down.

But by the time he had noticed the cotton thread his wife, Rosemarie, had arrived home and it was too late to take the baby back to the cellar. He made up the lie that Elisabeth had dumped the child on the doorstep and then gone back to the cult he alleged she had joined.

The diary also shows how Fritzl taunted his cellar children with photographs he took of their siblings in the garden or at a swimming pool.

By contrast, life underground grew almost unbearable in summer when soaring temperatures turned the warren of cells into an oven with condensation pouring down the walls.

"We are always happier when summer is over," wrote Elisabeth.

Prosecution spokesman Gerhard Sedlacek has confirmed Elisabeth's diaries are a vital part of the case against her father.

The diaries are believed to have allowed investigators to lock down the timing of key incidents in Elisabeth's life as her father's sex slave.