The release of more than 3,500 prisoners by the Cuban government is a "source of joy and spiritual relief," Catholic bishops in Cuba have said.

Ahead of Pope Francis' visit next Saturday, the Cuban government's goodwill gesture is the largest prisoner release since the 1959 revolution brought Fidel Castro to power.

Catholic bishops in Cuba have expressed their heartfelt satisfaction with the humanitarian move.

"The news of the liberation of prisoners is a source of joy and spiritual relief for the detainees themselves and their relatives as well as for the collaborators of the Prison Pastoral Care", said a statement from the General Secretariat of the Conference of Catholic Bishops of Cuba.

"With this action of mercy one is already anticipating the fruits that the visit of Pope Francis, as Missionary of Mercy, will leave for the welfare of all our people", it concluded.

Among those to be released are inmates older than 60, younger than 20 with no previous criminal history, the chronically ill, women and foreigners, providing their repatriation could be assured.

The pardons do not include the estimated 60 inmates who have been identified as political prisoners by the Commission of Human Rights and National Reconciliation.

Pope Francis' three day visit this month is part of Cuba's steadily improving diplomatic relations. The Catholic Church has maintained relations with Cuba since the revolution in 1959 and played a role in brokering a deal for restored relations with the United States.

However some Catholics in Cuba criticise the Church for failing to advocate on their behalf with the Cuban government. On Sunday the Cuban police detained about 50 people when the predominantly Catholic dissident group, Ladies in White, led a march in Havana.