Josef Fritzl yesterday broke his silence to give a jailhouse interview in which he defended his 24-year rape and imprisonment of his daughter.

He claimed he acted out of love when he imprisoned 18-year-old Elisabeth in a cellar, where she was repeatedly raped and gave birth to seven children.

Fritzl, 73, authorised his lawyer to put his side of the story to the Austrian magazine News. He also revealed details of the lies he told to mask his acts, the complicated electronic devices used to seal the concrete prison and how he managed to stock up on groceries, medicines and clothes for his victims without being discovered.

He said: "Ever since she entered puberty Elisabeth stopped doing what she was told, she just did not follow any of my rules any more. She would go out all night in local bars, and come back stinking of alcohol and smoke.

"She even ran away twice and hung around with persons of questionable moral standards, who were certainly not a good influence on her. I always had to bring her home, but she always ran away again. That is why I had to arrange a place where I gave her the chance - by force - to keep away from the bad influences of the outside world."

In the interview, published the day before Fritzl will be arraigned before magistrates in the first step of the process to determine whether he goes to jail or a psychiatric hospital, he denied claims that he had always been a tyrant at home, where he lived with his wife Rosemarie and children.

"I always put a lot of value on good behaviour and respect," he said. "I grew up in Nazi times and that meant the need to be controlled and respect of authority. I suppose I took on some old values.

"Yet despite that I am not the monster that I am portrayed as in the media."

However, asked how he would describe someone who kidnapped his own daughter, locked her away for 24 years and repeatedly raped her, he admitted: "On the face of it, probably a monster."

He admitted years of planning had gone into constructing the cellar with the intention of keeping his daughter there.

"I guess it must have been around 1981 or 1982 when I began to build a room in my cellar as the cell for her," he said. "I got a really heavy concrete and steel door that worked with an electric motor and a remote control that I used to get into the cellar. It needed a number code to open and close. I then plastered the walls, added something to wash in and a small toilet, a bed and a cooking ring, as well as the fridge, electricity and lights.

"Perhaps some people did notice what I was doing, but they really did not care. Why should they?"

On August 28, 1984, Fritzl locked Elisabeth in the cellar and ordered her to write letters telling her family that she had moved away and they were not to look for her. It was the start of a 24-year ordeal, during which she gave birth to seven children, three of whom were also forced to spend their lives in the cellar.

Elisabeth was only found on April 26 after her eldest daughter was admitted to hospital with an infection.

"I guess after the kidnap I got myself in a vicious circle, a vicious circle not just for Elisabeth but also for me from which there was no way out," Fritzl said.

"With every week that I kept my daughter prisoner my situation just got more crazy. I was scared of being arrested, and that my family and everybody that knew me would know my crime. That was why I kept putting off the day I should make a decision, putting it off again and again. Eventually, after a time, it was just too late to bring Elisabeth back into the world.

"My desire to have sex with Elisabeth also got much stronger as time went by. We first had sex in spring 1985. I could not control myself."

He added: "I always knew over 24 years what I did was not correct, and that I must be mad. Yet despite that, it just became a matter of course."

Elisabeth became pregnant for the first time in 1988 and gave birth in the cellar. She went on to have six other children, one of whom died.

Three of the babies were unwell after birth so Fritzl took them upstairs, where he and his wife cared for them.

He said Elisabeth and the three children in the cellar all had health problems and he would bring them medicine.

In 1998, he began to plan how to bring Elisabeth and her three children out of the cellar.

"I was getting older and knew in the future I would no longer be able to care for my second family," he said. "The plan was Elisabeth and the children would say they were kept by a sect in a secret place."

Asked if he thought this was realistic, and they would not betray him, he said: "Sure, that was my hope, however unbelievable at that time. Despite that, there was always the risk that Elisabeth and the children would betray me. That did happen rather sooner than I expected."