An emotional Oscar Pistorius spoke of his strong religious faith as he took the stand for the first time during his trial for killing Reeva Steenkamp.

In dramatic scenes at North Gauteng High Court in Pretoria, the fallen star said his faith had kept him going since Steenkamp's death and that he was "struggling a lot."

The 27-year-old admitted he has not returned to his house since 29-year-old Steenkamp was killed there on Valentine's Day last year.

Recalling his feelings for Steenkamp, Pistorius said: "I was taken aback by her and bowled over by how I felt about her."

Often fighting back emotions which threatened to overwhelm him, Pistorius said of Steenkamp: "I always wanted a partner who was a Christian. She was a very strong Christian, she always prayed for me about my training.

"It [his faith] is the thing that's got me through this last year. I've been struggling a lot. My god is my god of refuge," he said, before breaking down.

Presiding over proceedings, Judge Thokozile Masipa noted that Pistorius looked and sounded "exhausted."

Pistorius is in the fight of his life as he faces up to the prospect of spending at least 25 years in jail if he is convicted of pre-meditated murder.

The Olympian and Paralympian said: "I think there's a lot of things going through my mind and the weight of this is extremely overbearing so it's a lot of think about.

Pistorius also rvealed the death of his mother had caused him to struggle with his faith.

Under questioning by his lawyer Barry Roux, Pistorius described how he was brought up in the Anglian faith by his mother, while he father was often away working.

The Olympian and Paralympian denies murder and claims he mistook Steenkamp for an intruder inside his luxury home on the outskirts of Pretoria. The prosecution alleges he killed her following an argument between the couple.

The trial continues.