The Vatican says it will open its files relating to military rule in Argentina to victims and their relatives.
It says the decision has been taken at the request of Pope Francis “in the service of truth, justice and peace”.
Thousands of people were tortured, killed or disappeared during the period known as the Dirty War in Argentina from 1976 to 1983.
Many victims accuse the Roman Catholic Church of complicity and failure to speak out against abuses.
On Tuesday, the Vatican said that – together with Argentina’s bishops – it had finished digitizing the Church’s archives relating to the period.
It said the files would only be open to victims and their relatives, without setting a firm date.
The documents are being held in the Vatican’s secretariat of state, the Vatican’s embassy in Buenos Aires and also at the Argentine bishops’ conference.
Most of them would normally never be made public.
Pope Francis – who led Jesuits in his native Argentina under the junta and was known at the time as Cardinal Jorge Bergoglio – had pledged to open up the archives.
In 2013, the Vatican denied that the pontiff had failed to speak out against human rights abuses, saying “there has never been a credible, concrete accusation against him”.
Correspondents say that like other Latin American churchmen of the time, he had to contend, on the one hand, with a repressive right-wing regime and, on the other, a wing of his Church leaning towards political activism on the left.
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