Thirty-three political prisoners in Cuba have sent a letter to South African leader Nelson Mandela informing him that they will be celebrating the 20th anniversary of his liberation “from behind bars.”

The letter was written by prisoner of conscience and leader of the Christian Liberation Movement, Antonio Ramon Diaz Sanchez, who was condemned to 20 years in prison. Despite serious obstacles, 32 other prisoners were able to sign the letter, which recalls that with the liberation of Mandela on February 11, 1990, the world “witnessed the beginning of a process of change.”

This change, they wrote, put an end to an irrational social order and to “the repugnant regime of Apartheid.”

“We and many other Cubans, and you and many of your fellow countrymen, understand the pain of being imprisoned solely for wanting to contribute...nothing more than equality of rights and responsibilities for all citizens,” the letter stated.

One month and one week “following your 20th anniversary of release from prison, we will mark the seventh year of our unjust captivity.”  The prisoners explained they were arrested for urging peaceful change in Cuba and respect for human rights.

Similar to Mandela, the prisoners wrote, “we also are constantly accused of defending the interests and ideologies of foreign powers—an argument used to cover up political repression and justify long prison sentences.”

The Cuban prisoners expressed their solidarity with Mandela and sent their best wishes “to you and to all South Africans on this worldwide celebration of the 20th anniversary of the end of your captivity.”

The Christian Liberation Movement explained that only 33 prisoners could sign the letter because of communication difficulties. The movement then reaffirmed its “demand for the unconditional and immediate release of all Cuban political prisoners.”