Vatican City (AFP) - Pope Francis railed against social inequality Sunday, lamenting "the din of the rich few" drowning out the voice of the needy, as he marked the second "World Day of the Poor".

At a mass attended by about 6,000 poor people at St. Peter's Basilica in Rome, the pope noted that "injustice is the perverse root of poverty".

"The cry of the poor daily becomes stronger but heard less, drowned out by the din of the rich few, who grow ever fewer and more rich," he said ahead of a lunch at the Vatican for 1,500 destitute people and their helpers.

"Let us ask for the grace to hear the cry of all those tossed by the waves of life," the pope said.

"It is the cry of all those forced to flee their homes and native land for an uncertain future. It is the cry of entire peoples, deprived even of the great natural resources at their disposal... while the wealthy few feast on what, in justice, belongs to all."

The pope then had a lunch of lasagna, mashed potatoes and tiramisu with the poor in the immense Paul VI Hall, which adjoins the Vatican Basilica and usually hosts papal audiences and conferences.

The Vatican has also made available a team of doctors to provide free healthcare to the poor. Over 600 people were treated last year at the first World Day of the Poor, a tradition introduced by the pope.

Similar initiatives were held at other dioceses across Italy and elsewhere in the world.

The pope has often spoken about social inclusion, indirectly criticising governments that neglect those on the margins of society.