South African prosecutors said on Monday they would appeal the verdict and five-year jail term handed down to fallen track star Oscar Pistorius for killing his girlfriend last year.
"The decision to appeal both the conviction and sentence has been taken," said National Prosecuting Authority spokesman Nathi Mncube.
Pistorius began a five-year prison stretch on October 21 after being found guilty of culpable homicide, a charge equivalent to manslaughter.
Trial judge Thokozile Masipa found in September that there was not enough evidence to convict the 27-year-old Paralympic and Olympic athlete of premeditated murder.
Her verdict angered the state prosecution, which had sought to prove that Pistorius deliberately shot dead 29-year-old Reeva Steenkamp on Valentine's Day last year.
Steenkamp was shot four times through a locked toilet door at Pistorius' upmarket Pretoria home in the early hours of February 14, 2013.
Details of the appeal have not yet released, but Mncube said "the appeal on conviction is based on the question of law".
South African criminal lawyers had expressed shock that Masipa ruled Pistorius could not have foreseen that someone would die when he fired the shots that killed Steenkamp.
They complained that the ruling could open the door to systematic abuse of the legal system, or to people believing it would be okay to shoot in an irresponsible manner.
The double-amputee athlete alternatively told his lengthy trial in a Pretoria court that he believed there was an intruder and that he did not consciously fire his pistol.
"The merits and the demerits of the NPA's argument in this regard will become evident when we file papers for leave to appeal," said Mncube.
"The prosecutors are now preparing the necessary papers in order to be able to file within the next few days."
Question of intent
Lawyers said they were not shocked by the state's decision.
"It's not a surprise," said Wits University law professor Stephen Tuson, pointing to the question of intent or "dolus eventualis".
"It seems to me that there were questions that could be asked of the judgement in respect of the court's interpretation of dolus eventualis."
South Africans had also criticised Masipa's five-year sentence as too lenient after it emerged Pistorius may be eligible for parole in less than a year.
Reeva's mother June Steenkamp said in an interview with a British newspaper published on Sunday that she believed her daughter was about to leave Pistorius when he shot her dead.
"It was Reeva's bad luck that she met him, because sooner or later he would have killed someone," she added.
The state prosecution appeal sets the stage for another instalment of a legal battle that has gripped millions around the world.
Originally Pistorius's trial, which began in March, had been set to run for three weeks.
Almost eight months and a dedicated South African television channel later, Masipa handed down her verdict.
But the appeal is unlikely to see the same courtroom drama, with the proceedings instead being carried out by correspondence and without Pistorius being in attendance.
The case could be heard by the Supreme Court of Appeal in the central city of Bloemfontein or by a bench of three High Court judges.
Pistorius, the first double amputee Paralympian to compete against able-bodied athletes at the 2012 London Olympics, is currently being held at the Kgosi Mampuru prison in Pretoria.