VATICAN CITY — Pope Francis is urging the world to show a greater commitment to fighting human trafficking, which on Sunday he called “a form of modern slavery” and denounced as “brutal, cruel and criminal.”

The pope made the appeal during his traditional noontime Angelus prayer, on the U.N.’s world day against trafficking.

Francis said “every year, thousands of men, women and children are innocent victims of labor exploitation, and sex and organ trafficking.” He added that it has become something considered normal: “This is ugly. It is cruel. It is criminal.”

He called on the world to renew its commitment to battling “this abhorrent plague, a form of modern slavery,” and to pray that traffickers “change their hearts.”

The International Labor Organization estimates 21 million people are victims globally of forced labor, including victims of human trafficking for labor and sexual exploitation.

Pope Francis has targeted eradication of human trafficking as one of his papacy’s highest priorities. In May, for instance, he dispatched one of his top advisers, Bishop Marcelo Sanchez-Sorondo, to Baton Rouge, Louisiana, for the dedication of Metanoia Manor, a one-of-a-kind shelter for young trafficking victims.

“We need to recognize this crime against humanity and to combat this crime,” Sanchez-Sorondo said at the April 26 dedication, which drew more than 50 supporters on a sun-splashed spring day. “I think this is a grace of God to do all we can do to resolve and eradicate this form of slavery.”

Human trafficking has become an international concern, Sanchez-Sorondo noted, forcing an estimated 50 million victims into prostitution, sex slavery and other abusive behavior. He said 80 percent of the $32 billion generated annually through human trafficking is rooted in prostitution, with some of the girls as young as 12 and 13.

In April, Pope Francis sent a message to a conference on human trafficking organized by the Organization for Security and Co-operation in Europe (OSCE) in Vienna.

In that message, the pontiff called human trafficking a “form of slavery, a crime against humanity, a grave violation of human rights, an atrocious scourge, and it is all the more to be condemned when it takes place against children.”

The pope’s message to the OSCE was given by Father Michael Czerny, the under-secretary of the Migrants and Refugee Section of the Vatican’s new “Integral Development” office.

According to the dicastery’s statutes, the section concerning refugees and migrants will be temporarily under the pontiff, who will head it for as long as he considers it necessary.

“All too many children continue to be exploited, maltreated, enslaved, prey to violence and illicit trafficking,” Czerny told the organization, quoting the pope, “still too many children live in exile, as refugees, at times lost at sea, particularly in the waters of the Mediterranean.”

Czerny spoke about what is called the “three pillars” of fighting human trafficking: To prevent, to protect, to prosecute.

The priest said prevention can only happen by tackling both supply and demand, noting “several factors increase the vulnerability of the child victims, namely endemic poverty, inadequate child protection, ignorance and cultural constraints” in the places trafficking victims originate.

As for the second pillar – protection – Czerny said that both governments and NGOs have created “many remarkable initiatives” to ensure better protection of child victims of trafficking, but said these must emphasize the best interests of the child, “in which the family dimension occupies a place of greatest importance.”

Turning to the third “P”, prosecution, Czerny said “the complexity of the global human trafficking scenario” makes this very difficult, noting the movement from countries of origin, through transit countries, and finally to the countries of destination.

Quoting the pope, Czerny said “it is not possible to commit so complex a crime as human trafficking without the complicity, by action or omission, of states.

“While acknowledging the efforts of some countries to punish those responsible for such crimes, we must sadly note that there are still too few cases where ‘consumers’ have ended up in prison,” Czerny continued, “while perhaps not the masterminds, they are definitely the real authors responsible for such heinous crimes.”

Crux Staff also contributed to this report.