Nearly 90,000 Rohingya have fled to Bangladesh since violence erupted in Myanmar in August, pressuring scarce resources of aid agencies and communities already helping hundreds of thousands of refugees.
The bloodshed in Myanmar's northwestern Rakhine state was triggered by an attack on August 25 on dozens of police posts and an army base by Rohingya insurgents. The ensuing clashes and a military counter-offensive have killed at least 400 people.
Myanmar officials blamed Rohingya militants for the burning of homes and civilian deaths but rights monitors and Rohingya fleeing to neighbouring Bangladesh say the Myanmar army is trying to force Rohingya out with a campaign of arson and killings.
The treatment of Buddhist-majority Myanmar's roughly 1.1 million Muslim Rohingya is the biggest challenge facing leader Aung San Suu Kyi, accused by Western critics of not speaking out for the minority that has long complained of persecution.
The Nobel Peace Prize laureate has come under increasing diplomatic pressure from countries with large Muslim populations such as Bangladesh, Turkey, Indonesia and Pakistan to protect Rohingya civilians.
Myanmar says its security forces are fighting a legitimate campaign against "terrorists" responsible for a string of attacks on police posts and the army since last October.
The number of those crossing the border into Bangladesh - 87,000 - surpassed the number who escaped Myanmar after a series of much smaller insurgent attacks in October that set off a military operation beset by accusations of serious human rights abuses.
The newest estimate, based on calculations by UN workers in the Bangladeshi border district of Cox's Bazar, takes to nearly 150,000 the total number of Rohingya who have sought refuge in Bangladesh since October.
"We are trying to build houses here, but there isn't enough space," said Mohammed Hussein, 25, who was still looking for a place to stay after fleeing Myanmar four days ago.
"No non-government organisations came here. We have no food. Some women gave birth on the roadside. Sick children have no treatment."
An unofficial camp for Rohingya refugees that sprang up after the October attacks is being dramatically expanded.
