More than 300,000 Rohingya refugees from Myanmar have no adequate place to live in Bangladesh and are in need of emergency shelters, the International Organization for Migration (IOM) said Tuesday.

Tens of thousands of the Rohingya do not even have makeshift roofs over their heads and are camping in the open, exposed to monsoon winds and rain.

"We need to provide them with shelter immediately," said Mohammed Abdiker, the emergency operations chief of the U.N. organization based in Geneva.

The South Asian country has taken in more than 500,000 members of Myanmar's marginalized Muslim Rohingya minority since late August.

More than half a million Rohingya have fled from a Myanmar military crackdown in Rakhine State launched in late August that has been denounced by the United Nations as ethnic cleansing.

Rohingya Muslims in Bangladesh were sceptical on Tuesday about their chances of ever going home to Myanmar, even though the government there has given an assurance it would accept people verified as refugees.

The U.N. said it would seek $430 million to increase operations in the camps. Inside Rakhine, already one of Myanmar's poorest states, conditions are worsening for those left behind.

U.N. officials toured a conflict-hit portion of the state on Monday, noting the "unimaginable" scale of suffering and urging humanitarian access. An EU delegation accompanying them on the government-steered day trip urged an end to the violence after seeing "villages burned to the ground and emptied of inhabitants".

Bangladesh and Myanmar agreed on Monday to work on a repatriation plan, and a Myanmar government spokesman confirmed it would go along with it, provided people could verify their status with paperwork. But many refugees in camps in Bangladesh are scornful.

"Everything was burned, even people were burned," said a man who identified himself as Abdullah, dismissing the chances that people would have documents to prove a right to stay in Myanmar.

More than 10,000 Muslim Rohingya have massed in Myanmar near a crossing point into Bangladesh, Myanmar media said yesterday, apparently poised to join an exodus across the border due to food shortages and fear of attacks in their mainly Buddhist homeland.

Myanmar's northern state of Rakhine has been emptied of half of its Rohingya population in weeks. More are on the move as insecurity presses them to leave those villages which have so far been spared the worst of the violence that ripped through the state. Over 10,000 "Muslims" have arrived "between Letphwekya and Kwunthpin village to emigrate to the neighboring country", the state-backed Global New Light of Myanmar newspaper reported yesterday.

The U.N. has labeled the Rohingya one of the world's most persecuted religious minorities. Violence erupted in Myanmar's Rakhine state on Aug. 25 when the country's security forces launched an operation against the Rohingya Muslim community. It triggered a fresh influx of refugees towards neighboring Bangladesh, though the country sealed off its border to refugees. The region has seen simmering tension between its Buddhist and Muslim populations since communal violence broke out in 2012.