Oscar Pistorius will appear in a Pretoria court this afternoon after South African police opened a murder case against the Paralympic athlete.
Pistorius, 26, is suspected to have killed his 30-year-old girlfriend Reeva Steenkamp, who died of gunshot wounds at an address in the city this morning.
A 9mm pistol was recovered. According to unconfirmed reports, four shots were fired.
According to local media reports, Steenkamp may have been mistaken for an intruder at the property in the Silver Lakes Golf Estate in Boschkop in the capital Pretoria.
There was speculation the shooting may have been a Valentine's Day surprise gone wrong.
Miss Steenkamp, described in her Twitter biography as a model, cover girl and law graduate, had tweeted about Valentine's Day yesterday, writing: "What do you have up your sleeve for your love tomorrow??? #getexcited #ValentinesDay".
Police spokeswoman Lt Col Katlego Mogale told police were called to Pistorius's home early today following the shooting.
She said: "Paramedics declared the woman dead on the scene and police proceeded with their investigation. The woman sustained wounds to her head and the upper body."
"Currently we have opened the case of murder against a 26-year-old suspect.
"He will be appearing in Pretoria State Court this afternoon."
Mogale said police were called following a shooting at around 3am local time (1am Irish time) at a townhouse complex in the Silver Lakes district of Pretoria.
A pistol was recovered and the woman's body was removed from the scene.
Pistorius was arrested at the scene as investigations began.
Earlier, Mogale said: "I can confirm that a woman has been fatally wounded in a shooting at Oscar Pistorius' house. A 26-year-old man has been taken into custody."
Police responded quickly to an emergency call from a neighbour in the early hours but were unable to save the woman.
Brigadier Beukes said police were aware of media reports the death may have been an accident, caused by suspicions of a break-in, but said that those reports did not come from information provided by police.
“There was no sign of forced entry or persons who weren’t supposed to be there at this stage,” she said.
“The South African Police Service was surprised to hear allegations on the radio this morning that the deceased had been perceived to be a burglar. The allegations did not come from us.
“The deceased was a friend of his.”
She added: “There are witnesses and they have also been interviewed this morning.
“We’re talking about neighbours and people that heard things that happened earlier in the evening and when the shooting took place.”
Forensic tests were continuing on the premises.
Ahead of this afternoon’s court hearing, the spokeswoman said: “We will be opposing bail applications. The person will be bringing a bail application.”
Police have yet to name Pistorius as the man under arrest but said he was at the police station today.
The spokeswoman said of the man arrested: “At this stage there is no other suspect involved.”
She added: “There were only two people on the premises: the resident and the deceased.”
Pistorius is a national hero in South Africa and the world’s biggest star in Paralympic sport. The sprinter, nicknamed Blade Runner, won two gold medals and a silver at the London 2012 Paralympics.
Brigadier Beukes said police were aware of previous incidents at the house where Pistorius lives.
She said: “I can’t confirm that it’s related to the person who has been arrested, but I can confirm there has previously been incidents at the home of Mr Oscar Pistorius.”
Asked what they had been, Brigadier Beukes said they were “of allegations of a domestic nature”.
Double amputee Pistorius has emerged as the biggest star in the Paralympic movement and is known as the 'Blade Runner' because of the ground-breaking prosthetics he uses when competing.
He won two gold medals and one silver at the London 2012 Paralympics, having made history weeks earlier by competing in the Olympic Games for his country, becoming the first amputee sprinter to do so. He competed in the 400m and 4x400m relay at the Olympics.
The Johannesburg-born athlete, who was born without fibulas in his legs and had the limbs amputated below the knee when he was 11 months old, had to win a legal battle over his blades with the International Association of Athletics Federations (IAAF) in 2008 for the right to compete in able-bodied competition.
The International Paralympic Committee expressed sorrow on hearing of the incident.
In a statement, it said: "Following the news of the alleged shooting incident involving South African athlete Oscar Pistorius this morning, the International Paralympic Committee (IPC) will not be passing any comment on the case at this time.
"This is a police matter, with a formal investigation currently under way. Therefore it would be inappropriate for the IPC to comment on this incident until the official police process has concluded.
"The IPC would like to offer its deepest sympathy and condolences to all families involved in this case."