Oscar Pistorius breaks down in court-Apologises to Reeva's parents for killing their daughter..

A trembling Oscar Pistorius took the witness stand today, telling the court how the shooting of his girlfriend had left him terrified and plagued by nightmares which he wakes up from 'smelling blood'.

The track star also apologised for killing Reeva Steenkamp, saying he fired four times through a locked toilet door at his Pretoria home in the belief he was defending her from an intruder.

But his dramatic testimony was cut short after a couple of hours when his lawyers successfully argued that he was too emotionally exhausted to continue.

After leaving the box, he slumped down on the floor of the dock where he was comforted by his family and his psychologist who stroked his face to calm him down.

Earlier, with his voice cracking with emotion and fighting back tears, the Paralympian opened his testimony by addressing the model's mother June who stared back at him stony-faced from the public gallery.

'I want to take this opportunity to apologise to Mr and Mrs Steenkamp,' he said, at times barely audible as he sobbed.

'There hasn't been a moment since this tragedy happened that I haven't thought about your family.

'I wake up every morning and you're the first people I think of. The first people I pray for.

'I can’t imagine the pain and the sorrow and the emptiness that I’ve caused you and your family.

'I was simply trying to protect Reeva. I can promise you that when she went to bed that night she felt loved.

'I have tried to put my words on paper many times to write to you but no words would ever suffice.'

So sad!