Pope Francis has asked for forgiveness in the name of the Catholic Church for the mistreatment of the Roma people.
He made the comments during a meeting with Roma people at the last event of his three day trip to Romania, saying his heart was made "heavy" by the meeting.
"It is weighed down by the many experiences of discrimination, segregation and mistreatment experienced by your communities. History tells us that Christians too, including Catholics, are not strangers to such evil," he said.
With an estimated population of 10-12 million, approximately six million of whom live in the European Union, Roma people are the biggest ethnic minority in Europe and rights groups say they are often the victims of prejudice and social exclusion.
The pope’s comments are likely to increase tensions with Italy's anti-immigrant Interior Minister Matteo Salvini.
Mr Salvini, who has clashed with the pope repeatedly on migration issues, reacted angrily when Pope Francis received a group of Roma at the Vatican last month.
Mr Salvini, head of the far-right Lega party and a deputy prime minister, responded by repeating his promise to close all Roma camps in Italy.
"I would like to ask your forgiveness for this," the pope told the Roma. "I ask forgiveness – in the name of the Church and of the Lord – and I ask forgiveness of you. For all those times in history when we have discriminated, mistreated or looked askance at you ...".
A Roma youth, Razaila Vasile Dorin, told reporters: "It's an honour that a person like the pope comes to our community. We are proud."
Earlier on Sunday, the pope said a Mass for some 100,000 people during which he beatified seven Communist-era bishops of the Eastern Rite Catholic Church who died in prison or as a result of their harsh treatment during Romania's communist era.
"(The bishops) endured suffering and gave their lives to oppose an illiberal ideological system that oppressed the fundamental rights of the human person," Francis said.
After World War Two, Romania's Communist authorities confiscated properties of the Eastern Rite Catholic Church and ordered its members to join the majority Orthodox Church, which was easier for the party to control.
Historians say about half a million Romanians including politicians, priests, doctors, officers, land owners and merchants were sentenced and jailed in the 1950s and early 1960s and a fifth of them perished in prisons and labour camps.
Many Catholic properties taken by the Communist dictatorship or given by the government to the Orthodox have yet to be returned 30 years after the fall of dictator Nicolae Ceausescu.