BUENOS AIRES, DEC. 30 -- President Carlos Menem drew protests today as he made good on his widely criticized promise to pardon military officers who supervised the killing of some 9,000 Argentines and the torture of thousands more during the government's so-called "dirty war" against leftist political opponents in the late 1970s.

Menem announced six presidential decrees freeing Jorge Rafael Videla, Emilio Massera, Roberto Viola, Ramon Camps, Carlos Suarez Mason and several others -- all leaders or high-ranking officials of the military junta that held power from 1976 to 1983 and used its power to attempt to exterminate the far left.

Also released from prison by Menem's decrees was Mario Firmenich, a leader of the Montonero leftist guerrilla group, whose campaign against the state was cited as a justification for the armed forces' crackdown.

This evening, a crowd estimated at 40,000 rallied to protest the pardons.

Menem said he ordered the pardons to hasten "the definitive reconciliation of all the Argentine people." But polls have indicated that the pardons are highly unpopular, and immediate reaction from political leaders was overwhelmingly negative. Menem suffered no great political damage from a similar pardon a year ago, in which he absolved other officers accused or convicted of human-rights crimes. But this time the pardons cover the architects of the "dirty war," men who cannot say they were following orders.

"It is a lie that in order to achieve national unity, society must reconcile itself with crime," said former president Raul Alfonsin, whose administration oversaw the prosecution and sentencing of the junta leaders. "Death and violence are not proper political tools, and crimes committed with political motivation are still crimes."

Menem signed the pardon decrees Saturday but made no official announcement. Shortly before midnight, authorities at the Magdalena prison quietly began releasing their most famous inmates.

Videla, the army commander who led the 1976 coup overthrowing the hapless civilian regime led by Isabel Peron, had been serving a life sentence. Today, after his release, he went to Mass -- with reporters trailing behind -- and released an open letter to the current army chief of staff in which he called for "the revindication of the army and the restoration of military honor."

Viola, who succeeded Videla as head of the army and had been serving a 16-year term, said he wanted to spend the next few days with his family before making any public statements.

Firmenich, the Montonero leader, was spotted by reporters as he left the Villa Devoto prison near here. He led them on a high-speed chase through the city before finally making his getaway.

The mid-1970s was a time of great fear in Argentina. Isabel Peron's administration was collapsing and the Montoneros and other leftist groups were staging spectacular assassinations and kidnappings. Many Argentines welcomed the 1976 coup and gladly averted their eyes while the military went about ensuring that any leftist threat was eliminated.

Suspected leftists were pulled off the streets or out of their homes, never to be seen again. Some faced firing squads. Others were tortured to death in places like the Naval Mechanics School, their bodies loaded into helicopters to be dumped in the Plata River.

Camps, a former Buenos Aires police chief, and Suarez Mason, former commander of the First Army Corps, were major implementers of the junta's policies. Of the 9,000 Argentines believed killed, more than half were taken into custody in Suarez Mason's jurisdiction.

After democracy returned to Argentina in 1983, the new civilian government conducted Nuremberg-style investigations and trials. The first official testimony heard publicly from a victim was that of Adriana Calvo de Laborde, a physics professor at the University of La Plata. Today, the left-leaning daily Pagina 12 reprinted portions of her stunning account. Seven months' pregnant, she was dragged from her house and kept blindfolded in an interrogation center for a month, along with other prisoners, whose screams kept her awake. When she went into labor, her guards finally agreed to take her to a hospital, but she ended up giving birth to her daughter -- unassisted -- in the back of a moving car.

Her interrogators never told her why she had been arrested, although they did ask questions about a friend of her husband, who had visited Chile during the period when the Socialist Salvador Allende was president. "I honestly do not think even they knew why I was being held," she said of the men who asked her questions.

The pardons are meant to cool simmering resentment within the armed forces over the way the military was treated after democracy returned. There have been four military uprisings -- the most recent less than a month ago -- in which rebel officers' demands centered at least partly on the desire for vindication.