South African Olympic and Paralympic runner Oscar Pistorius will appear in court tomorrow after being charged with murdering his girlfriend in Pretoria.

Police opened a murder case after a 30-year-old woman was found dead at the athlete's house after an incident in the upmarket Silverlakes gated complex on the outskirts of the capital.

Mr Pistorius and his girlfriend, Reeva Steenkamp, had been the only people in the house at the time of the shooting, police brigadier Denise Beukes told reporters.

Witnesses have been interviewed about the incident, which happened in the early hours of the morning.

"We are talking about neighbours and people that heard things earlier in the evening and when the shooting took place," she said.

Ms Beukes said police were aware of previous incidents at the Pistorius house.

"I can confirm that there has previously been incidents at the home of Mr Oscar Pistorius, of allegations of domestic nature," she said.

His lawyer Kenny Oldwage told SABC TV that Mr Pistorius is "doing well but very emotional", and gave no further comment.

Earlier, police said a 9mm pistol had been found at the scene.

Mr Pistorius was born without a fibula in both legs and races wearing carbon fibre prosthetic blades.

He was the first double amputee to run in the Olympics and reached the 400 metre semi-finals in London 2012.

Before the murder charge was announced, Johannesburg's Talk Radio 702 said the 26-year-old may have mistaken Ms Steenkamp for a burglar.

South Africa has some of the world's highest rates of violent crime, and many home owners have weapons to defend themselves against intruders.

Mr Pistorius' complex is surrounded by a 3m wall and electric fence.

In 2004, Springbok rugby player Rudi Visagie shot dead his 19-year-old daughter after he mistakenly thought she was a robber trying to steal his car in the middle of the night.