A UN report has said top military figures in Myanmar must be investigated for genocide in Rakhine state and crimes against humanity in other areas.
The report, based on hundreds of interviews, is the strongest condemnation from the UN so far of violence against Rohingya Muslims.
It says the army's tactics are "grossly disproportionate to actual security threats". Myanmar rejected the report.
At least 700,000 Rohingya fled violence in the country in the past 12 months.
The report names six senior military figures it believes should go on trial and sharply criticises Myanmar's de facto leader, Nobel Peace Prize laureate Aung San Suu Kyi, for failing to intervene to stop attacks.
It calls for the case to be referred to the International Criminal Court (ICC).
The government has consistently said its operations targeted militant or insurgent threats but the report says the crimes documented are "shocking for the level of denial, normalcy and impunity that is attached to them".
"Military necessity would never justify killing indiscriminately, gang raping women, assaulting children, and burning entire villages," the report says.
The UN mission did not have access to Myanmar for its report but says it relied on such sources as eyewitness interviews, satellite imagery, photographs and videos.
Harder to dismiss now
Genocide is the most serious charge that can be made against a government and is rarely proposed by UN investigators.
That this report finds sufficient evidence to warrant investigation and prosecution of the senior commanders in the Myanmar armed forces is a searing indictment which will be impossible for members of the international community to ignore.
However taking Myanmar to the ICC, as recommended by the report, is difficult. It is not a signatory to the Rome Statute that established the court, so a referral to the ICC would need the backing of the permanent five Security Council members - and China is unlikely to agree.
The report suggests, instead, the establishment of a special independent body by the UN, as happened with Syria, to conduct an investigation in support of war crimes and genocide prosecutions.
The government of Myanmar has until now rejected numerous investigations alleging massive atrocities by its military. This one will be much harder to dismiss.
What crimes does the UN allege?
The UN's Independent International Fact-Finding Mission on Myanmar was set up in March 2017 to investigate widespread allegations of human rights abuses in Myanmar, particularly in Rakhine state.
It began its work before the military started a large-scale operation in Rakhine in August of last year, after deadly attacks by Rohingya militants.
Seeing through the official story in Myanmar
The situation was a "catastrophe looming for decades", the report argues, and the result of "severe, systemic and institutionalised oppression from birth to death".
Crimes documented in Kachin, Shan and Rakhine include murder, imprisonment, torture, rape, sexual slavery, persecution and enslavement that "undoubtedly amount to the gravest crimes under international law".