Pope Francis criticized rising wealth inequality and the treatment of migrants on Sunday, saying the world should not ignore those "tossed by the waves of life".

"Injustice is the perverse root of poverty," Francis said at a Mass marking the Roman Catholic Church's annual World Day of the Poor. "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."

Francis also reiterated his support for migrants saying that people must pay attention to "all those forced to flee their homes and native land for an uncertain future".

His remarks came as hundreds of migrants from a caravan of Central Americans were stalled at the U.S.-Mexico border after being denied entry to the United States, although Francis made no direct reference to the situation in the United States.

A report this year by Oxfam said 3.7 billion people, or half of the global population, saw no increase in their wealth in 2017, while 82 percent of the wealth generated last year went to the richest one percent of the global population.

Pope Francis plans to visit Morocco in March next year, a two-day trip that is likely to highlight the plight of migrants, given the kingdom's role as a transit route for Africans looking to migrate to Europe.

The Vatican announced the trip on Tuesday, saying the Pope had accepted an invitation from King Mohammed VI and would visit the north African country on March 30 and 31, stopping in Rabat and Casablanca. It gave no more details.

The Pope told Reuters in an exclusive interview this year that Europe needed to focus on education and investment in Africa if it wanted to stem the flow of migrants.

As Italy closes its ports to most African asylum-seekers, more are entering Spain with the majority coming via Morocco.

Morocco is a destination in itself and has granted 56,000 residency permits to foreigners, mostly from Sub-Saharan Africa, since it reformed its migration policy in 2013.