It is the first time it has been confirmed that the athlete has run since he was charged with the Valentine's Day shooting death of girlfriend Reeva Steenkamp.
A grainy cellphone photo of what appears to be Pistorius on the track at the University of Pretoria was published Thursday on the front page of the Afrikaans-language Beeld newspaper in South Africa.
The photograph — taken by a high school student from a bus passing by the track — shows the double amputee at some distance wearing his unmistakable blades and dark lycra running clothes and walking on a track with his hands on his hips.
In response to the newspaper's claim that Pistorius had begun training as much as two weeks ago, his family denied that he was on "any official training program" and had only been out running "on a number of isolated occasions."
"Each time has been very difficult and he has struggled immensely with the decision to even leave the house," Arnold Pistorius, Oscar's uncle, said in the statement.
But the family had encouraged Pistorius to get back on the track, his uncle said.
The photo was taken on March 24 by teenager Lisa Smith, her field hockey coach said, when their team was visiting the University of Pretoria, where Pistorius' regular practice facility is.
The Associated Press reported on Wednesday that Pistorius had been at the track in the South African capital on the day of the photograph and had done some jogging. It was the first time Pistorius had pulled on his running blades since he shot Steenkamp dead in his home in the early hours of Feb. 14, his agent, Peet van Zyl, told the AP later on Thursday.
Pistorius was only "having a jog around the track," the agent reiterated, as the newspaper claimed sources had told it the Olympic 400-meter runner and Paralympic champion had begun full training at the university on March 21. Van Zyl disputed that and said neither he nor Ampie Louw, Pistorius' coach and the man who controls his training sessions, were present at the track on the day the photograph was taken.
Field hockey coach and school sports director Charmaine Koekemoer said she was driving the bus past the track at around 10.15 a.m. on the Sunday morning when members of her Hoerskool Voortrekker girls hockey team started shouting "There's Oscar! There's Oscar!" from the back.
Student Smith then took the photo on her BlackBerry, Koekemoer said. It shows Pistorius in the distance with the bars of a metal fence in the foreground. He is the only person in the shot and is walking in front of empty, gray spectator stands.
"The kids were very excited," Koekemoer told the AP. "That was the excitement, seeing a world icon in real life. It was nothing to do with his case.
"We didn't see him running around the track. He was just walking to the 100 meter end line down the final stretch. It looked like he was going to take his blades off."
The single photo, taken through the black fence and showing Pistorius walking on the far side of the track, was accompanied by a front-page story in Beeld under the headlines "Oscar is back on the track" and "In training with other athletes."
Pistorius' management team was expecting news of the athlete's run to become public, Van Zyl said, after Pistorius had told them he had visited his track with some Australian athletes on that day. Koekemoer — who was visiting with her students from their school in the eastern city of Pietermaritzburg — said there were other athletes around Pistorius when they saw him.
Neither Pistorius' coach nor his agent knew about the track visit until afterward, Van Zyl said.
But while Pistorius has not yet returned to a training routine, the agent said, his return could be any day now and the image of the world's most famous disabled athlete back on his running blades was likely to become more and more common again.
"He might get up this morning and call (coach) Ampie (Louw) and say he wants to be at the track at one o'clock," Van Zyl said. Van Zyl also said Pistorius' desire to start training again did not show disrespect to the family of Steenkamp.
Arnold Pistorius, the uncle, also appeared to be readying the world for the return of his nephew to running on track regularly, even though he was still "extremely traumatized" by the death of Steenkamp.
"We all encouraged him to get back onto the track to help stabilize him emotionally," Arnold Pistorius said. "We encourage him to start exercising as we believe it is a vital step in helping him deal with the trauma."
Oscar Pistorius denies murder in the Valentine's Day killing of model Steenkamp, saying he mistook her for a nighttime intruder in his home. His next scheduled court appearance is June 4, when prosecutors say they intend to serve indictments.
Follow Gerald Imray at www.twitter.com/GeraldImrayAP