The Olympic sprinter was treated for minor wrist injuries and returned to his prison cell in Pretoria on Saturday, said Singabakho Nxumalo, a spokesman for South Africa's Correctional Services.
Pistorius' brother, Carl Pistorius, tweeted Sunday that the disgraced athlete had "slipped in his cell and injured himself, nothing serious."
He had just visited his brother, who was "doing well given the circumstances," he tweeted.
He said that he was aware that "there are reports saying that he had tried to injure himself -- they (are) completely untrue and sensational."
Pistorius denied speculation of a suicide attempt, Nxumalo said. He declined to provide additional details, citing privacy concerns.
Pistorius killed Reeva Steenkamp
at his home in an upscale Pretoria neighborhood in the early hours of Valentine's Day three years ago, firing four bullets through a bathroom door.
Pistorius has maintained the killing was an accident after he mistook her for an intruder, while the prosecution said he killed her deliberately after the two had an argument.
He was originally convicted of manslaughter in 2014 after months of hearings.
But in December, a higher court overturned the conviction, saying the original ruling was flawed, and found Pistorius guilty of murder.
A judge sentenced Pistorius to six years in prison
last month. South Africa's National Prosecuting Authority said it intends to appeal the six-year prison sentence
, calling it "shockingly too lenient."
Before Steenkamp's killing, Pistorius was internationally renowned as a boundary-breaking sprinter.
Born without fibulas in either leg, he had both legs amputated below the knee in his first year of life, but raced using carbon-fiber prosthetic blades that earned him the nickname the "Blade Runner."
A champion Paralympian athlete, with six gold medals to his name, he became the first double-amputee athlete to compete against able-bodied runners in the Olympics in 2012.