By Mark Dummett
BBC News, Dhaka
Many refugees lack adequate food and sanitation
An international aid agency has accused Bangladesh of launching a violent crackdown against unregistered Rohingya refugees from Burma.
Medecins Sans Frontieres (MSF) also warned of a humanitarian crisis unfolding in a squatter camp where a growing number of them now live.
But the government body responsible has dismissed the MSF allegations.
Rohingya repatriation commissioner Firoj Salauddin told the BBC there had been "no crackdown" against them.
"If the police find any Rohingyas without passports or any identity cards, they arrest them according to the law of the country," he said.
Thousands of refugees have moved to the camp in fear of persecution, MSF says.
It says doctors at its clinic have treated the victims of beatings by the police and Bangladeshi citizens.
Many Rohingyas - some of whom have lived peacefully in Bangladesh for three decades - complain that their houses were destroyed and border guards had attempted to force them to leave the country.
But district police chief Kamrul Ahsan told the BBC that only those Rohingyas in the country illegally had been arrested.
"The number is very few, two or three in a month," he said.
MSF says about 6,000 people have arrived in the Kutupalong camp from other parts of south-east Bangladesh since October, when the crackdown started.
"People are crowding into a crammed and unsanitary patch of ground with no infrastructure to support them," said Paul Critchley, MSF head of mission for Bangladesh.
"Prevented from working to support themselves, neither are they permitted food aid. As the numbers swell and resources become increasingly scarce, we are extremely concerned about the deepening crisis," he said.
A report, released this week by the Arakan Project, a Bangkok-based lobby group, made similar claims.
"A major humanitarian catastrophe is unfolding for the unprotected Rohingya in Bangladesh," it said.
The Rohingyas are Muslims from north-west Burma who speak a dialect of Bengali.
They are among the world's least wanted and most persecuted people - Burma denies them citizenship and refuses to let them own land.
It does not allow them to travel or even marry without first seeking permission.
And they are not welcome in Bangladesh either, where at least 200,000 now live as illegal immigrants, without rights to employment, health care or education.
The region in which they live is one of Bangladesh's poorest and local communities complain that the Rohingya drain the area of resources, take away their jobs and are involved in smuggling and other crimes.
Some 30,000 have been registered as refugees by the UN, but the rest have no rights and mostly live in dreadful conditions on the edge of Bangladeshi villages or in squatter camps.
MSF is calling on the Bangladesh government and UNHCR to offer them much greater protection.