A former Argentine navy captain has gone on trial in Buenos Aires for his alleged involvement in the disappearance and torture of dissidents during the country's 1976 to 1983 military dictatorship .

Alfredo Astiz, known as the "Blond Angel of Death," is accused of multiple crimes that include the killings of two French nuns and the disappearance of an Argentine journalist.  Eighteen other former military officers are also on trial with Astiz in the Argentine capital.

Astiz was tried and convicted in absentia by a Paris court in 1990 for the nuns' murders.  They were apparently kidnapped and killed for helping anti-government activists in Argentina.

Official estimates say some 13,000 people died or disappeared during the military crackdown on leftist activists known as the "dirty war."  Human rights groups put the toll at 30,000.