Bignone is accused of holding ultimate responsibility for cases of torture, illegal break-ins and deprivations of freedoms from 1976 to 1978, before he was appointed president by the military junta in the waning years of the dictatorship.

As president from 1982 to 1983, it fell to Bignone to protect the military as Argentina returned to democracy. He granted amnesty to human rights violators and ordered the destruction of documents related to torture and disappearances of political opponents before agreeing to transfer power to the democratically elected Raul Alfonsin.

Argentina's courts and congress eventually overturned the amnesty, and President Cristina Fernandez has made a priority of prosecuting leaders of the dictatorship. Bignone was charged in 2003 but is only now being tried in open court.

The trial is being held in a small indoor stadium to accommodate a crowd that on Monday included witnesses, federal officials, activist groups and family members of the disappeared who carried signs and photos of the victims.

Taty Almeida, co-founder of the Mothers of the Plaza de Mayo rights group, said her 20-year-old son Alejandro was kidnapped by security forces and killed at Campo de Mayo, allegedly on orders from Gen. Santiago Mar Riveros, the base's intelligence chief. She called the trial a historic accomplishment.

"They should at least get a life sentence, which is what they deserve for those abominable crimes," Almeida told The Associated Press. "We can't forgive and forget. We won't rest until the last of them has been served justice."

On trial along with Bignone and Riveros are four other former generals, a former colonel and a former police commissioner.

Bignone and Riveros have denied responsibility for the crimes in past court proceedings, and they are scheduled to make declarations beginning later this week after all the charges are read.

The trial is expected to last through February, said Pablo Llonto, one of the victims' lawyers. Nearly all the defendants are in their 80s and are being held under house arrest.

An official report listed 13,000 people killed during the 1976-83 dictatorship. Human rights groups say 30,000 died.

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Associated Press Writer Almudena Calatrava contributed to this report.