A Peruvian court on Wednesday annulled ex-president Alberto Fujimori's pardon for crimes against humanity and ordered the 80-year-old's immediate arrest, officials said.
The South American country's justice department said in a statement that the Supreme Court had "issued the arrest and detention orders against former president Fujimori so that he may be re-integrated into the prison establishment."
Fujimori was pardoned by presidential decree last December. He was 12 years into a 25-year jail sentence handed down to him over his ordering of two massacres by death squads between 1991 and 1992.
The pardon, issued by then-president Pedro Pablo Kuczynski before he was himself brought down by a corruption scandal, triggered a wave of protests by human rights organizations and by victims of Fujimori's crackdown.
Fujimori, a Peruvian of Japanese descent, has been living in Lima but has been hospitalized four times since his release last December.
Victims of Fujimori's crackdown had petitioned the Inter-American Court to demand a judicial review of the process that led to the pardon.
Carlos Rivera, a lawyer for the victims, said the decision to annul the pardon was justified.
"Kuczynski's pardon to Alberto Fujimori has no legal value and therefore he has to return to prison for irregularities in the process," he said.
Kuczynski had justified the pardon on humanitarian grounds, given Fujimori's well-documented ill-health.
"International standards in the humanitarian pardon were not met," Rivera said.
Alejandro Aguinaga, Fujimori's doctor, expressed shock at the news. "We see that in Peru nothing is respected. The pardon of president Fujimori was a constitutional action," Aguinaga told Chilean radio RPP.
Fujimori has had a number of operations as part of a long-running battle with tongue cancer. His most recent hospitalization was in August, for an irregular heartbeat.
He has been working on a memoir about his decade in power (1990-2000), a period marked by corruption but also by a fight against guerrillas and terrorism.
"I have reached 80 bearing the marks of the years, with all the shocks of political life, the enormous satisfactions and the profound regrets," he wrote in a message to AFP around his birthday in July.
"In the few years I have left," Fujimori explained in his handwritten text, "I will dedicate myself to three objectives: bringing my family together, improving my health to the extent possible, and striking a serene and balanced equilibrium in my life."
However, Fujimori has been unable to reconcile his daughter Keiko, 43, who heads the right-wing Popular Force party, with her 39-year-old brother Kenji, who leads a rival faction of the party, to end a political schism which could see the two face off in the 2021 presidential elections.
The charge of crimes against humanity stemmed in part from the killings or disappearances of scores of civilians -- allegedly by a shadowy squad of military officers -- during Peru's bloody struggle against Maoist rebels.
The ex-ruler is revered and despised in equal measure in Peru. Admirers laud him for dragging the country's economy into the modern era and defeating the Shining Path guerrilla movement.