Thousands of Rohingya are continuing to flee violence and persecution in Burma and crossing into Bangladesh, where more than half a million others are already living in squalid and overcrowded camps, according to witnesses and drone footage shot by the UN office for refugees.

The UNHCR video shot Monday shows thousands of Rohingya trudging along a narrow strip of land alongside what appears to a rain-swollen river in the Palong Khali area in southern Bangladesh.

Witnesses said that a new wave of refugees started crossing the border over the weekend.

An Associated Press photographer saw thousands of newcomers near one border crossing Tuesday.

Several said that they were stopped by Bangladeshi border guards and spent the night in muddy rice fields.

Local government administrator Mohammad Mikaruzzman said Tuesday that he heard some 20,000 people have arrived since Sunday, crossing the border on foot or by boat at several points.

According to the UN some 537,000 Rohingya refugees have arrived in Bangladesh since violence erupted there on August 25.

The exodus has continued, with a few small breaks, over the last eight weeks.

The new arrivals, almost all terrified and starving, have described scenes of incredible violence, with army troops and mobs of Buddhist locals attacking Rohingya homes.

The UN has described the violence in Burma's Rakhine state as "textbook ethnic cleansing".

More recent refugees have also said the Rohingya were being starved in a bid to make them leave.

A woman who spoke to The Associated Press on Tuesday after her arrival said they had had no food to eat.

"We came here two nights ago with lot of difficulties. It took us eight days to reach here," said Anjuma, who gave just one name.

Several refugees said Bangladesh border guards were not letting them move toward the refugee camps and they were forced to spend a night out in the open in pelting rain.