Disgraced former Peru president Alberto Fujimori was admitted to hospital suffering from an irregular heartbeat, the country's social security agency said on Tuesday.
Upon his arrival at a hospital in Lima late on Monday night, "medical staff managed to stabilize" the 84-year-old former leader, Essalud said in a statement.
Fujimori, who is serving a 25-year sentence for crimes against humanity, was then transferred to an observation room.
His doctor, Alejandro Aguinaga told RPP radio station that Fujimori, who has been in prison since 2007, had registered a "paroxysmal atrial fibrillation," a type of irregular heartbeat.
Fujimori was also taken to hospital in April last year for a similar problem.
Fujimori suffers recurrent respiratory, neurological and hypertension problems.
President from 1990 to 2000, Fujimori was subsequently jailed over massacres committed by army death squads in 1991 and 1992 in which 25 people were killed in supposed anti-terrorist operations.