About 18,000 Rohingya Muslims have fled fresh violence in Burma and crossed into Bangladesh, with hundreds stranded in no man's land at the border, according to the International Organisation for Migration.
Sanjukta Sahany, a spokeswoman for the IOM in Cox's Bazar, on the border, released the latest figures as human rights groups and advocates for the Rohingya said the Burmese army was retaliating for attacks by Rohingya militants by burning villages and shooting civilians.
The Burmese government blames Rohingya insurgents for the violence, including the arson. The official death toll in the violence was 96 as of Sunday, but the true number is likely to be higher.
A majority of Burma's estimated one million Rohingya live in the northern part of Rakhine state, where they have faced persecution in the Buddhist-majority country.
Last week, Rohingya insurgents launched co-ordinated attacks against police posts, provoking retaliation by government forces.
Ms Sahany said the Rohingya crisis was not an issue between Burma and Bangladesh but of international concern.
Ali Hossain, Cox's Bazar district's senior government official, said resources are under huge stress with 87,000 Rohingya entering Bangladesh since last October and now another 18,000 in one week.
"I have already informed the government's high-ups about the trouble we are facing here," he said. "This is a very complex situation."
In another development, police said a boat carrying an unknown number of Rohingya capsized in the Naf River, leaving at least four dead.
The boat was trying to enter Bangladesh through Shah Porir Island in the Bay of Bengal when it sank, said police official Main Uddin.
He said rescuers recovered four bodies and "most probably" many others were missing.
"Our search is on. We don't know how many were on the boat," he said.
Bangladesh's border guards have turned back 171 Rohingya after detaining them at different border points over the last two days, said Colonel SM Ariful islam.
He said border guards provided food and medicine before pushing them back, but it was not clear what happened to them later.
Burma refuses to recognise Rohingya as a legitimate native ethnic minority and has denied citizenship and rights to most of them.