"Despite the numerous warnings I've made of the risk of atrocity crimes, and the worldwide community has buried its head in the sand".
The mission's report was based on over 600 in-depth interviews with victims and witnesses.
At the Naypyitaw news conference, Myanmar officials sought to counter accusations heard at the UN Human Rights Council this week.
U Aung Hla Tun, Myanmar's deputy minister of information, said on Wednesday that the Rohingya exodus to Bangladesh was caused, in part, by threats from the Rohingya insurgents who carried out fatal raids on Myanmar security posts on August 25. "Others were hacked to death", the experts told the human rights council.
In her statement, Lee said that actions in the country "bear the hallmarks of genocide".
A man crosses a bamboo bridge over rice paddies in the Chakmakul camp for Rohingya refugees in southern Bangladesh on February 13. The campaign of violence by the military has seen thousands killed, Rohingya villages burned to the ground and hundreds of women raped and abused.
Adama Dieng spent a week in Bangladesh to assess the condition of the nearly 700,000 Rohingyas who had fled across the border from Myanmar, and he said during his trip he heard "terrifying stories".
In Myanmar, Ashin Wirathu, an ultranationalist Buddhist monk who preaches hate against the Rohingya, has been able to build up large followings on social media - using Facebook to spread divisive and hate-fueling messages. "Importantly, it will be impossible for anyone to claim where they are from or describe where they had previously lived if the region's landscape has been so significantly altered".
U Zaw Htay, a Myanmar government spokesman, said on Wednesday that repatriated individuals would spend no more than a month in the camps.
On Monday, UN Special Rapporteur on the human rights situation in Myanmar, Yanghee Lee, said in Geneva that the Myanmar government led by Aung San Suu Kyi must be held accountable together with the military for the crimes committed against the Rohingyas, Efe news reported.
Social media has "substantively contributed to the level of acrimony and dissension and conflict", Darusman told reporters on March 12.
"Nobody should be allowed to politicise this repatriation process", he said, and called on the global community and the media to help Myanmar in making the repatriation process successful.
"I'm afraid that Facebook has now turned into a beast, and not what it originally intended", she said, replying to a question about the merit of the social media platform in the country, which began transitioning to a democracy in 2011.
Speaking to the Human Rights Council on Monday, the United Nations special rapporteur on human rights in Myanmar, Yanghee Lee, said that "the repressive practices of previous military governments were returning as the norm once more" in Myanmar.