Human Rights Watch urged world leaders to impose sanctions on Myanmar’s military, which is accused of driving out more than 400,000 Rohingya Muslims in an orchestrated “ethnic cleansing” campaign.

The call from the rights group came as the United Nations General Assembly prepared to convene in New York.

Myanmar had hinted Sunday it would not take back all who had fled across the border, accusing those refugees of having links to the Rohingya militants whose raids on police posts in August triggered the army backlash.

Any moves to block the refugees’ return will likely inflame Bangladesh Prime Minister Sheik Hasina, who 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.

According to AFP,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 in a statement.

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.

Myanmar’s civilian leader Aung San Suu Kyi is preparing in a televised speech Tuesday to address the nation on the crisis for the first time.

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.