Pressure grew on Myanmar on Monday as a rights group urged world leaders to impose sanctions on its military, which is accused of driving out more than 400,000 Rohingya Muslims in an "ethnic cleansing" campaign.
The call from Human Rights Watch came as the UN General Assembly prepared to convene in New York, with the crisis in Myanmar one of the most pressing topics.
The exodus of Rohingya refugees from mainly Buddhist Myanmar to neighbouring Bangladesh has sparked a humanitarian emergency. Aid groups are struggling to provide relief to a daily stream of new arrivals, more than half of whom are children.
There are acute shortages of nearly all forms of aid, with many Rohingya huddling under tarpaulins as their only protection from monsoon rains.
Myanmar hinted on Sunday that it would not take back all those who had fled across the border, accusing the refugees of having links to the Rohingya militants whose raids on police posts on August 25 triggered the army backlash.
Any moves to block the refugees' return is likely to anger Bangladesh, whose prime minister Sheikh Hasina will urge the General Assembly to put more global pressure on Myanmar to take back all the Rohingya massing in shanty towns and camps near the border.
Human Rights Watch also called for the "safe and voluntary return" of the displaced as it urged governments around the globe to punish Myanmar's army with sanctions for the "ongoing atrocities" against the Rohingya.
"The United Nations Security Council and concerned countries should impose targeted sanctions and an arms embargo on the Burmese military to end its ethnic cleansing campaign against Rohingya Muslims," the group said.
It called on the General Assembly to make the crisis a priority, urging countries to impose travel bans and asset freezes on Myanmar officers implicated in the abuses, as well as to expand arms embargoes.
Myanmar's army was hit with sanctions during its 50-year rule of the country. Most have been lifted in recent years as the generals have allowed a partial transition to democracy.
"Burma's senior military commanders are more likely to heed the calls of the international community if they are suffering real economic consequences," said John Sifton, HRW's Asia advocacy director.
As Rohingya flee Myanmar, Suu Kyi skips UN General Assembly
Myanmar's civilian leader Aung San Suu Kyi is preparing to address the nation on the crisis for the first time in a televised speech on Tuesday.
The Nobel peace laureate has angered the international community with her near-silence on the plight of the Rohingya and her failure to condemn the actions of the army, with whom she has a delicate power-sharing arrangement.
Speaking to the BBC over the weekend, UN secretary general Antonio Guterres called her upcoming address a "last chance" to stop the unfolding humanitarian calamity.
Until now her government has defended the military campaign as a legitimate crackdown on the Rohingya militants, who first emerged as a fighting force last October.
On Sunday Myanmar's Information Committee accused those who fled to Bangladesh — more than a third of the Rohingya population — of working with the Rohingya militia, a rag-tag group of fighters armed with mostly rudimentary weapons.
"Those who fled the villages made their way to the other country for fear of being arrested as they got involved in the violent attacks," it said.
"Legal protection will be given to the villages whose residents did not flee."
The violence has gutted large swathes of northern Rakhine in just over three weeks, with fires visible almost daily across the border from the Bangladesh camps.
Some 30,000 ethnic Rakhine Buddhists and Hindus have also been displaced by the unrest.
While the world has watched the refugee crisis unfold with horror, there is little sympathy for the Rohingya inside Myanmar.
Many Buddhists revile the group and have long denied the existence of a Rohingya ethnic group, insisting they are illegal immigrants from Bangladesh.