Argentina's former military dictator Reynaldo Bignone has been handed a 15-year prison sentence for more crimes he committed at a secret detention center during the 1976 military coup. Argentina's 2nd Oral Federal Court handed down the ruling on Thursday, sentencing Bignone for human rights violations and crime against humanity. The former ruler was given the 15-year prison term for overseeing the takeover of the Posadas de Haedo hospital in Buenos Aires and setting up "Chalet" -- a notorious detention center -- where leftist opponents were allegedly tortured. Bignone, 83, has already been sentenced to a life term for the torture and murder of political opponents during Argentina's 1976-83 military regime. He is also serving 25 years behind bars for abduction, torture and murder of 56 people held at the Campo de Mayo military base outside Buenos Aires more than three decades ago. Bignone served as de facto president of Argentina from 1982 to 1983, when he turned over power to democratically-elected president Raul Alfonsin. Human rights groups estimate that as many as 30,000 people were killed or made to disappear during military rule, which waged a "dirty war" against the left.