Pope Francis has sent a special message to support the work of prison chaplains during the Year of Mercy.

"He especially wishes to assure all who are serving prison communities of his prayerful solidarity and deep gratitude for their efforts in upholding the human dignity of all those incarcerated," Cardinal Pietro Parolin, the Vatican Secretary of State, said to a European meeting of chaplains June 1.

The Pope also thanked prison chaplains for helping the incarcerated to celebrate the Year of Mercy. The observance includes the establishing of Holy Doors in various churches and prisons to help encourage growth in grace.

The Roman Pontiff specifically reflected on how prisoners can use Holy Doors in prisons in his September 2015 letter about the Year of Mercy.

"May the gesture of directing their thought and prayer to the Father each time they cross the threshold of their cell signify for them their passage through the Holy Door, because the mercy of God is able to transform hearts, and is also able to transform bars into an experience of freedom," the Pope had said.

In his latest message, the Pope sent his greetings to the participants of the European meeting of prison chaplains at the Council of Europe in Strasbourg, May 30-June 1. The meeting focused on a pastoral view of radicalization in prisons.

Cardinal Parolin concluded the papal message, saying: "With these sentiments, Pope Francis willingly invokes upon you and all gathered the divine blessings of peace and joy."

The chaplain meeting organizers include the Council of European Bishops' Conferences, the International Commission of Catholic Prison Pastoral Care, and the Permanent Mission of the Holy See.