Burma has subjected Rohingya Muslims to long-term discrimination and persecution that amounts to "dehumanising apartheid", Amnesty International has said in a report.
The document also raises questions about what those who have fled a violent military crackdown would face if they returned home.
Since late August, more than 620,000 Rohingya have fled Burma's Rakhine state into neighbouring Bangladesh, seeking safety from what the military described as "clearance operations".
The United Nations and others have said the military's actions appeared to be a campaign of "ethnic cleansing", using acts of violence and intimidation and burning down homes to force the Rohingya to leave their communities.
UN secretary-general Antonio Guterres said earlier this month that the world body considered it "an absolutely essential priority" to stop all violence against the Rohingya and allow them to return to their homes.
They are now living in teeming refugee camps in a Bangladesh border district, and officials in Dhaka have also urged that Burma allow them to return with their safety assured.
Burma leader Aung San Suu Kyi said today the government would follow a formula set in a 1992-93 repatriation agreement between Bangladesh and Burma, which are holding bilateral negotiations on the new refugee crisis.
Amnesty International compiled two years' worth of interviews and evidence in its report, detailing how Rohingya lived within Burma, where they were subjected to a "vicious system of state-sponsored, institutionalised discrimination that amounts to apartheid", meeting the international legal definition of a crime against humanity.
Rohingya have faced state-supported discrimination in the predominantly Buddhist country for decades.
Though members of the ethnic minority first arrived generations ago, Rohingya were stripped of their citizenship in 1982, denying them almost all rights and rendering them stateless.
They cannot travel freely, practice their religion, or work as teachers or doctors, and they have little access to medical care, food or education.
Amnesty's report, issued on Tuesday, said the discrimination had worsened considerably in the last five years.
"I wanted to go to Sittwe hospital for medical treatment, but it's forbidden," Abul Kadir, 36, was quoted as telling the human rights group.
"The hospital staff told me I couldn't go there for my own safety and said I needed to go to Bangladesh for treatment.
"It cost a lot of money."
Rohingya have fled en masse to escape persecution before.
Hundreds of thousands left in 1978 and again in the early 1990s, though policies subsequently allowed many to return.
Communal violence in 2012, as the country was transitioning from a half-century of dictatorship to democracy, sent another 100,000 fleeing by boat.
Some 120,000 remain trapped in camps outside Rakhine's capital, Sittwe.
Rohingya were thought to number around one million people in Burma until late last year.
That October, a Rohingya militant group killed several officers in attacks on police posts, and the military retaliation sent 87,000 Rohingya fleeing.
A larger militant attack on August 25 killed dozens of security forces, and the military response was swift and comprehensive.
By the tens of thousands, Rohingya began fleeing, their villages set aflame, some of the survivors bearing wounds from gunshots and land mines.
Though the waves of refugees are now thinner, people are still crossing the Burma border nearly three month later.