Two former Argentine dictators have been convicted of systematic baby stealing crimes from political prisoners three decades ago.

Jorge Videla, 86, and Reynaldo Bignone, 84, were found guilty of their charges on Thursday by an Argentine court in Buenos Aires.

Videla had been sentenced to 50 years while Bignone received 15 years of prison.

Both Videla and Bignone are already serving life imprisonments for human rights violations.

The two were accused of carefully drafting plans for the systematic stealing of new born babies of Leftist activists. The babies were then handed over to the military-supported families and raised while their original mothers were killed. At least 400 to 500 babies are believed to have been stolen by the military juntas.

Videla ruled the country from 1976 to 1981, and the last dictator of Argentina, Bignone ruled from June 1982 to December 1983.

"It was the worst, the most perverse of the dictatorship, I think, what they did with us. It was a torture prolonged through time, for the grandmothers searching, for family members, everyone," the CNN quoted Francisco Madariaga Quintela, one of the stolen babies who was reunited with his father after three decades, in 2010.

The campaign for justice and reunite the lost children was led by the Grandmothers of Plaza de Mayo.

People inside the courtroom cheered when the verdict was pronounced.

The dictators argued that they did not steal the babies and the insurgents were using the babies as human shields in their fight against their regime.

Of the 11 former military rulers and officials who were charged with the crime, nine including Videla and Bignone were found guilty. They were found guilty of the theft of 34 babies - Videla was convicted of the theft of 20 babies alone.

British journalist Robert Cox who was actively reporting the crimes during those periods was a key witness in the trial in 2011.

He said: "the kidnapping of newly-born babies is the last crime that former members of the military regime are willing to admit. It's like the Nazis, what they did was so terrible they could never admit it".

"It was a plan because they set up these maternity wards expressly for that purpose in the camps were they held opponents. They try to make it sound as if they were being humane in saving the kids, but the kidnapping of babies is the one thing that even the most right-wing fascist-minded supporters of the dictatorship condemn," Cox told The Guardian.