But it wasn't until Thursday that the UN Security Council held its first public meeting on the situation in more than eight years.
UN Secretary-General Antonio Guterres told the council that the current outbreak of violence has "spiraled into the world's fastest-developing refugee emergency, a humanitarian and human rights nightmare."
"We've received bone-chilling accounts from those who fled, mainly women, children and the elderly," he said.
Their forced migration constitutes the quickest exodus
from a single country since the Rwandan genocide in 1994.
Rohingya Muslims are considered to be among the world's most persecuted people. The predominantly Buddhist Myanmar considers them Bangladeshi, but Bangladesh says they're Burmese. As a result, they're effectively stateless.
On August 25, Rohingya militants killed 12 security officers in coordinated attacks on border posts, according to Myanmar's state media. In response, the military intensified "clearance operations" against "terrorists," driving thousands of people from their homes.
The security council meeting came as 15 Rohingya, including nine children, drowned after their boat sunk while trying to escape Myanmar to Bangladesh across the Bay of Bengal.
US ambassador to the United Nations told the Security Council Thursday Myanmar's actions in Rakhine State appeared to be ethnic cleansing, an allegation UN human rights chief Zeid Raad al-Hussein first made weeks ago.
The government of Myanmar has repeatedly denied this, claiming security forces are carrying out counter attacks against "brutal acts of terrorism."
In a statement, the country's foreign ministry
claimed that security forces are taking "full measures to avoid collateral damage and the harming of innocent civilians."
Visiting Myanmar National Security Advisor U Thaung Tun blamed terrorism, not religious persecution, for the unfolding crisis. He said there is "no ethnic cleansing or genocide" in Myanmar, adding that those charges should not be lobbed lightly.
Despite the harsh words no formal action was taken after the session. Ambassadors said they felt that the 15-member council sent a strong message to Myanmar.
Haley: Time for words has passed
During Thursday's meeting, Ambassador Haley said the time for "well meaning words in the Council have passed."
She said that action must be considered against "Burmese security forces who are implicated in abuses stoking hatred among fellow citizens," and urged countries that now sell weapons to Myanmar to suspend their deliveries until the military provides accountability.
Haley called for the Myanmar military to respect human rights and fundamental freedoms.
"Those who have been accused of committing abuses should be removed from command responsibilities immediately and prosecuted for wrongdoing," she said.
Before the meeting, Amnesty International called for an arms embargo on Myanmar. The group says Myanmar has torched entire villages inside Rakhine State and fired on people trying to flee.
Myanmar issued an invitation to the UN Secretary-General to come visit the country in the "near future." The UN said that it's studying the offer.
The Myanmar envoy also said diplomats accompanied by media will visit northern Rakhine state on Monday.
The UN does not have its own army, and it has gotten nowhere with pleas for diplomacy. A UN team set to tour Rakhine state on Thursday found its trip cancelled -- due to the weather, according to Myanmar.
Guterres: 'End the military operations'
The UN Secretary-General proposed three things for the Myanmar government to do.
"First, end the military operations," Guterres said. "Second, allow unfettered access for humanitarian support. And third, to ensure the safe voluntary and sustainable return of the refugees to their areas of origin."
Japan's UN Ambassador Koro Bessho strongly condemned the attacks on civilians and said his nation was deeply disturbed at reports of killings.
Myanmar's special envoy told the Council the country realizes the humanitarian situation needs to be addressed. He said thousands fled because of fear due to terrorism, and that Myanmar is cooperating with the Red Cross.
The UN Secretary-General warned that "we should not be surprised if decades of discrimination and double standards in treatment of the Rohingya create an opening for radicalization."
China, a neighbor of Myanmar and Bangladesh where hundreds of thousands have fled, said "there is no quick fix" to the conflict.
Diplomats say they want a political dialogue to start. The Council plans to hear from former UN Secretary-General Kofi Annan, who chaired a commission on Myanmar packed with recommendations, next week.
Swedish UN Ambassador Olof Skoog said the Annan report "provides the way forward," as he urged the Myanmar government to take responsibility to bring an end to the conflict once and for all."