More than 20,000 Rohingya Muslims fled from Myanmar to Bangladesh in recent weeks escaping a renewed wave of violence, humanitarian officials said on Tuesday.

Bangladeshi border patrols stepped up efforts to turn back refugees, but about 21,000 Rohingya entered the country over the past two months, said Sanjukta Sahany, the head of the International Organization for Migration office in Bangladesh's southeastern district of Cox Bazar that borders Rakhine.

"It is based on the figures collected by UN agencies and international NGOs [non-governmental organizations]," she told AFP.

The Dhaka office of the United Nations High Commissioner for Refugees separately estimated that "there could be 21,000 new arrivals in recent weeks," in a statement.

Rohingya refugees in Bangladesh described acts of gang-rape, torture and murder by Myanmar's security forces who began a bloody crackdown in October in the state of Rakhine.

Solidarity groups estimated several hundred members of the stateless ethnic minority were killed since October.

The United Nations estimated more than 30,000 have been displaced. Most moved into makeshift settlements, official refugee camps and villages, Sahany said.

They killed us mercilessly

Young mother, Mohsena Begum, 20, said Myanmar soldiers came to her village of Caira Fara in the morning and set fire to the concrete-and-thatch homes. Soldiers shot anyone who fled into the fields, she said.

A group of soldiers and local men allegedly slit the throats of four village leaders and then beat and raped her. 

Arabic teacher Osman Gani, said he fled after his village, Gouzo Bil, was attacked on November 11.

"They came and killed mercilessly. They burned our homes," he said at the weekend near the Naf River. "No one was there to save us."

Human Rights Watch said satellite images showed hundreds of buildings in Rohingya villages had been razed.

The latest outbreak of violence began after a series of attacks on guard posts near the Bangladesh border that killed nine police officers. Security forces swept the state searching for unidentified attackers.

Myanmar's leader and Nobel peace laureate Aung San Suu Kyi vowed to work for"peace and national reconciliation," last week, but did not mention the violence in Rakhine state. In a recent TV interview she accused the international community of stoking unrest.

"It doesn't help if everybody is just concentrating on the negative side of the situation, in spite of the fact that there were attacks on police outposts," she said on Singapore's Channel News Asia.

aw/ (AFP, dpa AP)