Despite Bangladesh’s immigration laws disallowing unregistered entrants from crossing the border into their nation from neighboring countries, thousands of Rohingya Muslims have fled their homes in Myanmar, seeking refuge in the Southeast Asian nation. A United Nations spokesman, John McKissick, announced on Thursday that the international organization believes the Myanmar government has been ethnically cleansing the Muslim minority group from the Rakhine State.

Myanmar, also known as Burma, launched a massive security operation in the region in October following the attack and murder of nine police officers on border posts in Maungdaw.  A militant group in the area tied to the Rohingya people has been blamed for the attacks, leading to counterinsurgency operations that sealed off the Maungdaw district of the state.

Activists from within the Muslim minority group claim that more than 100 people have already been killed, with hundreds more detained in retaliation for recent attacks on the police.

Officials within the Myanmar government have confirmed reports that Rohingya Muslims have been fleeing the area, claiming that they are setting fire to their own houses as they go to cover their departure. They also contested the United Nation’s claims regarding their counterinsurgency offensive in the area.

Myanmar’s presidential spokesman, Zaw Htay, said the U.N. spokesman “should maintain his professionalism and his ethics as a United Nations officer, because his comments are just allegations.” He went on to say, “He should only speak based on concrete and strong evidence on the ground.”

Bangladesh’s foreign ministry reached out to the Myanmar ambassador on Wednesday to express their “deep” concerns about the military operations in the region, as well as the “desperate people” crossing their border to seek safety. Bangladesh formally requested that Myanmar make efforts to “ensure the integrity of its border” through the ambassador’s office.

Satellite images of the area show more than 1,200 homes have been burned in Rohingya villages over the past six weeks. Whether those fires were set by the Myanmar government or the Rohingya Muslims themselves—as the government has claimed—cannot be confirmed because journalists and aid workers have been barred from the Rakhine State in Myanmar.

Although the Myanmar government asserts that the United Nations’ claims are false, McKissick, who serves as the head of the U.N. refugee agency on the Bangladeshi border, seems utterly certain.