Pope Francis has ordered the Vatican to open its files on Argentina’s military dictatorship, a move that could help the families of thousands of victims of the military regime finally discover the fate of their loved ones.

“This is the pope’s wish – for something to be done – so he has asked the secretariat of state to take charge of it, and work has already begun on declassifying the Vatican archives related to Argentina’s dictatorship,” Father Guillermo Karcher, an Argentinian priest who is a close aide of the pope, said in an interview with a Buenos Aires radio station.

During the 1976-83 dictatorship, 20,000 people were made to “disappear” by the Argentinian authorities, who saw them as subversives. The Vatican collected a large amount of information on these cases, principally through the papal nuncio’s office in Buenos Aires.

The pope acceded to the opening of the Vatican archives at a meeting last week with Lita Boitano, the 83-year-old mother of two sons who were “disappeared” during the dictatorship.

“Pope Francis told me the Vatican will open its archives for that period,” Boitano, president of the Argentinian human rights group Familiares (“Relatives”), said after her meeting with the pope in Rome.

The pope – who was born in Buenos Aires – arranged a meeting between Boitano and Monsignor Giuseppe Laterza, an official in the Vatican secretariat of state, at which they also discussed the possibility of the Vatican issuing a statement of self-criticism regarding its role during Argentina’s dictatorship, Boitano said.

The most important documents to be released could be the reports wired to Rome by the Vatican’s then ambassador to Buenos Aires, Monsignor Pio Laghi, who met regularly with the military chiefs. Laghi even played tennis on a regular basis with the navy’s then commander-in-chief, Admiral Emilio Massera, considered to have been one of the bloodiest members of the three-man military junta that ruled Argentina with an iron fist.

The Vatican also collected information from victims’ families, who turned to Monsignor Laghi for help. The nuncio’s office kept files on the thousands of disappearances reported by relatives and pleaded to the military for clemency, often acting as a go-between in specific cases.

“It’s not a promise, it’s a certainty, and it is extremely important,” said Graciela Lois in Buenos Aires, another member of Familiares who lost her husband Ricardo to the dictatorship. “This also shows a side of Pope Francis that not many realise is there,” Lois added. “You must remember that during the dictatorship he was close friends with Esther Careaga, one of the Mothers of Plaza de Mayo [the mothers of the disappeared who confronted the military about the abuction of their children].”

The pope, then Jorge Bergoglio and head of the Jesuit order in Argentina during the military regime, maintained his friendship with Careaga despite her revolutionary ideals and her harsh criticism of the regime. Careaga was finally “disappeared” herself in December 1977 when the regime cracked down on the Mothers of Plaza de Mayo.

“It was a very positive meeting,” said Boitano regarding her meeting with Francis. “He promised us he would take care of the matter. The church had the exact data on the disappearances and the Vatican is looking for it.”

“The collection of the material has been concluded and there is a system to scan and digitise it,” Monsignor Laterza of the secretariat of state told the Italian newsagency Ansa. “It could be available to the public in one year.”

Speaking to the Guardian from Rome today where she continues meeting with Vatican officials, Boitano recalled how in her years in exile in Europe during the dictatorship she became aware first-hand of how much information on the “desparecidos” the Vatican had.

“In 1979 I was in Rome and had asked for a meeting with Pope John Paul II, which I didn’t get, but I got a meeting with a Vatican official. When I gave him my name, he left and quickly returned with a file card with my name on it. It had all the details of my two kids and the exact dates of their kidnappings, they knew exactly who I was.”

During her one-and-half-hour meeting with Laterza, Boitano pleaded for an immediate opening of the archives after Laterza told her it would take at least one year till the work is completed. “I told him I am 83 years old and that most of the mothers and fathers of the “disappeared” who are still left alive are over 80 years old as well. We can’t afford to wait any longer.”