YANGON, Myanmar -- The Vatican on Wednesday defended Pope Francis after human rights groups expressed disappointment that he didn't publicly acknowledge the plight of Rohingya Muslims, who have been subject to what the United Nations has termed a campaign of "textbook ethnic cleansing" by Myanmar's military.

Spokesman Greg Burke said Francis took seriously the advice given to him by the local Catholic Church, which urged him to toe a cautious line and not even refer to the "Rohingya" by name during his trip to Myanmar and Bangladesh, since the majority of people in Myanmar reject the term because the ethnic group is not a recognized minority in the country.

"The moral authority of the pope stands," Burke asserted Wednesday. "You can criticize what's said, what's not said, but the pope is not going to lose moral authority on this question here."

Burke spoke as Francis neared the midpoint of his weeklong trip, which was in the works well before the Myanmar military launched what it called "clearance operations" in Rakhine state in response to attacks by a group of Rohingya militants against security positions in August. The campaign, denounced by the U.N. and the U.S. as "ethnic cleansing," has forced more than 620,000 Rohingya to flee to neighbouring Bangladesh in the worst Asian refugee crisis in decades. Rohingya in the camps have reported entire villages in Myanmar being burned and looted and women and girls raped.

Burke noted that the Holy See had only recently established diplomatic relations with Myanmar, that the Catholic Church in the country was small, and that the Holy See's broader gains were to "build bridges" with the predominantly Buddhist nation as it emerges from decades of military dictatorship.

"Everyone is entitled to their opinion. Vatican diplomacy is not infallible," Burke said. At the same time, he stressed that Francis' diplomatic stance in public in Myanmar didn't negate what he had said in the past, or what he might be saying in private.

In the past, Francis has strongly condemned the "persecution of our Rohingya brothers," denounced their suffering because of their faith and called for them to receive "full rights." And he has defined his papacy by his outspoken defence of refugees and advocacy for society's most marginal and disenfranchised. While he called in his first major speech on Tuesday for all of Myanmar's ethnic groups to have their human rights respected, his failure to specify the Rohingya crisis on Myanmar soil drew criticism from Amnesty International, Human Rights Watch and Rohingya themselves.

Myanmar's government and most of the Buddhist majority say the members of the Muslim minority are "Bengalis" who migrated illegally from Bangladesh and don't acknowledge them as a local ethnic group even though they have lived in Myanmar, also known as Burma, for generations.

Burke and senior members of Myanmar's Catholic Church spoke to reporters after Francis had a busy day stressing a message of forgiveness, unity and healing of old wounds during an open-air Mass, an audience with Myanmar's senior Buddhist monks and during an encounter with his own Catholic bishops.

Local authorities estimated that about 150,000 people turned out for the Mass, but the crowd seemed far larger and included faithful bearing flags from Thailand, Cambodia and Vietnam, among other places.

In his homily, Francis acknowledged the suffering that Myanmar's ethnic and religious groups have endured, a reference to the decades of conflicts between Myanmar's military and ethnic minorities who seek greater autonomy. The conflicts involving the Karen, Kachin, Sha and Wa -- who are 40 per cent of the country's population -- have claimed thousands of lives and continue today in parts of the country.

"I know that many in Myanmar bear the wounds of violence, wounds both visible and invisible," Francis said at the Mass in Yangon's Kyaikkasan Ground park. While the temptation is to respond with revenge, Francis urged instead a response of "forgiveness and compassion."

Aung San Suu Kyi's civilian government, which came to power in 2015 after decades of military rule, has been negotiating with 17 of the 20 major ethnic groups, a process Francis and the Myanmar Catholic Church have sought to encourage.

A prayer read out in the Karen language during the Mass referred directly to the initiative. "For the leaders of Myanmar, that they may always foster peace and reconciliation through dialogue and understanding, thus promoting an end to the conflict in the states of Kachin, Rakhine and Shan, we pray to the Lord," read the prayer.

Members of Myanmar's mostly Christian Kachin minority were on hand for the Mass, many of whom travelled two days by train from Kachin state to see the first pope ever to visit Myanmar.

Despite the high humidity, the scene at the park was joyous and pious, with many women covering their heads with lace veils.

"I can't express how happy I am," said Henery Thaw Zin, a 57-year-old ethnic Karen from Hinthada, a four-hour drive from Yangon. "I can't imagine, or can't expect to get a chance like this again, not just in this life, but in my next life as well."

Later Wednesday, in a meeting with Myanmar's senior Buddhist monks, Francis called for religious leaders to speak with one voice affirming their commitment to peace and respect for justice and dignity for all people.

"If we are to be united, as is our purpose, we need to surmount all forms of misunderstanding, intolerance, prejudice and hatred," Francis told the Sangha council, a committee of high-ranking monks appointed by the government.

Citing the teachings of both Buddha and his namesake, St. Francis of Assisi, Francis said: "May that wisdom continue to foster patience and understanding and heal the wounds of conflict that through the years have divided people of different cultures, ethnicities and religious convictions."

The head of the council, Bhamo Sayadaw, lamented how some people use religion for "extremism and terrorism," saying such interpretations were wrong and inspired by "greed and ego" since religion is meant to inspire the common good.

The elderly monk didn't refer to any particular religion, but the government has identified a group of Rohingya Muslim militants as a terrorist group, while the Sahgha council has denounced Myanmar's growing Buddhist nationalist group, which has used hate speech to inspire violence against Muslims.

And in his final event of the day, Francis met with his bishops in Yangon's Catholic cathedral, and urged them to help their tiny flock heal from "deeply rooted divisions" that have scarred the country, and help foster unity.

Francis wraps up his visit to Myanmar on Thursday with a Mass for young people in the cathedral before heading to Bangladesh for the second and final leg of his weeklong South Asia tour.

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Htusan reported from Bangkok. Associated Press producers Hau Dinh and Min Kyi Thein contributed to this report.