Three Cuban political prisoners were freed Wednesday and a leading human rights advocate said he believed their liberation was part of a U.S.-Cuban deal to release 53 dissidents.

The head of Cuba's Human Rights and Reconciliation Commission, Elizardo Sanchez, told The Associated Press that 19-year-old twins Diango Vargas Martin and Bianko Vargas Martin were released without any of the judicial procedures that normally precede the liberation of those held in politically related cases. He said Wednesday night that Enrique Figuerola Miranda had just been freed under similar circumstances.

The releases followed days of mounting criticism in the U.S. of a rapprochement between Cuba and Washington that included an agreement on the release of 53 prisoners that the Obama administration wanted released.

According to Amnesty International, the brothers were arrested in December 2012 as they tried to return to their home, where they lived with their mother, a member of the dissident group Ladies in White. They had been held on charges of using violence or intimidation against a state official. Amnesty described them as prisoners of conscience.

All three lived in the far eastern city of Santiago and are members of the Patriotic Union of Cuba, a small dissident group considered to be the country's most vehemently anti-government. Figuerola had been held since July 2012 on the same charge as the Vargas brothers.

Sanchez said he believed that the three releases were the start of a wider liberation of political prisoners. Neither Cuban nor U.S. officials commented Wednesday night.

U.S. officials said last month that Cuba agreed to free 53 people considered by Washington to be political prisoners who it wanted freed as part of negotiations to restore full diplomatic relations. Since then, neither Cuba nor the United States has publicly given out any of the names on the list and no releases have been announced, prompting swelling criticism in the U.S. of the secretive deal between Presidents Barack Obama and Raul Castro.

Francisco "Pepe" Hernandez, president of the Cuban American National Foundation, said he had been informed by the White House that Lady in White member Sonia Garro, her husband and a neighbor had been let go as part of the deal prior to both governments' Dec. 17 announcement of warming relations.

Sanchez said he had no official confirmation that the Vargas Martin brothers were on the list of 53 prisoners, but the facts of their release led him to believe their release was part of the U.S.-Cuba deal.

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"They're prisoners of conscience and they've been freed immediately and with no conditions," he said.

Associated Press writer Michael Weissenstein contributed to this report.