Pope Francis is celebrating an important Latin American feast day with a Mass featuring Argentine folk hymns.

The Argentine pope has praised the "Misa Criolla," one of the first Masses composed in the vernacular after the liberating reforms of Vatican II. He has said the Spanish-language hymns, haunting and accompanied by folk percussion, were an important step in the church's development in Latin America.

The feast of Our Lady of Guadalupe is one of the region's most important holidays. Millions of people make the pilgrimage to a Mexican basilica to honor the dark-skinned virgin who is said to have appeared to an Indian peasant Dec. 12, 1531.

The late Argentine composer Ariel Ramírez presented "Misa Criolla" to Pope Paul VI on the same feast day 50 years ago.