The agency says thousands of people who fled, fearing reprisals by the Myanmar military, reportedly are stuck along the Myanmar side of the border.
Thousands of Muslims have been killed over the last three days in Myanmar's western Rakhine state. "We took an oath to save Arakan [another name for Rakhine], even if it is with sticks and small knives", one insurgent in Bangladesh near the border told AFP.
"All the people want to follow the army to get out of here".
There are already nearly 400,000 Rohingya refugees in Bangladesh in squalid camps near its border with Myanmar. On Friday, she condemned the raids in which insurgents wielding guns, sticks and homemade bombs assaulted 30 police stations and an army base.
Some 3,000 people have attempted to flee to Bangladesh but Myanmar has tightened its borders.
Amnesty International have accused Myanmar's mainly Buddhist military of murder, rape, torture and looting in the Rohingya's northern state of Rakhine.
"They've already said it", he said.
Of the 1.1 million Rohingya in Rakhine state, about 120,000 live in internally displaced persons camps near the Rakhine capital Sittwe where they were sent following deadly communal violence with Buddhists in 2012.
The government said it was investigating whether global non-government organization staff were involved when militants surrounded and blockaded a village in August.
UNHCR spokesman Adrian Edwards told VOA his agency can not confirm the reports.
"It does not hear and it does not see", he added. He would visit the Bangladeshi capital, Dhaka, from November 30 to December 2. I would like to express my full closeness to them - and let all of us ask the Lord to save them, and to raise up men and women of good will to help them, who shall give them their full rights.
For Myanmar's national leader Aung San Suu Kyo, hailed the country's saviour when elected in the credible poll for 25 years, the army's treatment of the Rohingya and her failure to stop it blights her records and worldwide reputation. Rohingya Muslims, however, have had roots in the country that go back centuries.
Satellite images revealed the large scale burning of Rohinyga villages in Myanmar's Rakhine State on Tuesday, as United Nations secretary general Antonio Guterres expressed "deep concern" over reports of civilian killings.
"Extremist terrorists blew out improvised bombs, set fire the villages and attacked the police outposts in Region-2 of Maungtaw yesterday from the morning to afternoon", an English-language statement issued by the Information Ministry said.
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