Argentina's President, Nestor Kirchner, has led a ceremony to mark the 30th anniversary of the coup that brought the military to power for seven years.
Thousands of people are still missing, presumed dead
He unveiled a plaque with the words "Never Again" in Buenos Aires.
Mr Kirchner also called on the judiciary to decide what action to take over the remaining immunity laws for Argentina's former military leaders.
Big crowds have gathered in the capital for a march to mourn the tens of thousands of victims of the coup.
At least 30,000 people were killed in what was known as the Dirty War. Many of the bodies have never been recovered.
Speaking at the Military College, Mr Kirchner said there could be "no reconciliation if any trace of impunity remained".
"The justice system has already declared [the pardons] unconstitutional in some concrete cases... And now, it is the judiciary that must determine whether the pardons are valid or constitutional," he said.
After he unveiled the plaque, a minute of silence was held to honour the victims.
In Buenos Aires, more than 3,500 photographs of victims were projected onto the Obelisco monument. Thousands of people sang protest songs and watched newsreel footage of coup leaders on large screens.
The BBC's Daniel Schweimler reports from the city that the 30th anniversary seems to have struck a chord like no other in Argentine society.
The Mothers of Plaza de Mayo, who held weekly protests for much of the past 30 years to demand justice for their children, held an all night vigil ahead of Friday's commemorations.
"We all want to be present to say 'never again' to military dictatorship," said Argentine Nobel Peace Prize winner Adolfo Perez Esquivel.
Plaques listing the victims of the Dirty War have been unveiled at work places and in parks. And there have been art exhibitions, poetry readings and debates around the country.
A small protest marred the day's celebrations
There was a brief, violent protest when more than 100 youths clashed with police while demonstrating outside the apartment of dictatorship-era Economy Minister Jose Alfredo Martinez de Hoz.
The government announced this week that all military archives would be opened to the public. It is hoped they may shed some light on unsolved cases.
Mr Kirchner has overturned laws granting amnesty to top officers and is waiting for courts to rule whether the amnesties are constitutional before ordering prosecutions.
He has also said presidential pardons given to officers tried in 1985 will be cancelled.