Argentina's Supreme Court on Tuesday struck down two amnesty laws shielding military officers from human rights prosecutions, clearing the way for hundreds to be tried for abductions, torture and killings committed during what came to be known as the country's "dirty war."

The high court declared the laws unconstitutional in a 7-to-1 vote with one abstention, scrapping the amnesties that ended trials for atrocities carried out under Argentina's 1976-83 military dictatorship.

A government report says 11,000 people died or disappeared during a systematic crackdown by the military to snuff out dissent. Human rights groups say the number is closer to 30,000.

The ruling marked a victory for those groups, which have been seeking a reexamination of the military's seven-year rule. It also highlighted a new political will under President Nestor Kirchner, who was held briefly by the military when he was a student, for investigating dirty war abuses.

Dozens of human rights activists, including some gray-haired mothers who have led a decades-long search for many of those who disappeared, cheered the decision outside the main Buenos Aires courthouse after it was announced.

The decision came in the case of Julio Simon, a former police officer charged in connection with the disappearance of two Argentines and the adoption of their daughter.

Under Argentine law, Tuesday's ruling was expected to serve as a precedent for other cases in lower courts.

Lawyers for human rights groups said the decision could lead to new charges against 300 to 400 military officers, many of them now retired.

Jose Miguel Vivanco, executive director of the Americas division of Human Rights Watch, said he hoped the ruling would encourage such other South American countries as Uruguay, Chile and Colombia, where amnesty laws now exist or are under debate.

After Argentina's return to democracy in 1983, many ranking military officers were tried on charges of human rights violations against suspected opponents and ordered imprisoned two years later.

But after a series of military uprisings, Raul Alfonsin, then the president, sought a pair of amnesties from Congress in a bid to temper anger in the barracks.

The laws ended the investigations of the military junta's top officials and protected lower-ranking officers from prosecution on the grounds they were legally compelled to carry out orders.

In 1990, President Carlos Menem issued a pardon for all military officials in an attempt at what he called "national reconciliation."

Many of the junta's top leaders, including Jorge Videla, a former general, and Emilio Massera, an admiral, are under house arrest on charges of kidnapping babies born to mothers held in captivity during the military rule.