The number of Rohingya Muslims fleeing to Bangladesh in the last two weeks to escape the violence in Myanmar has shot up to about 270,000, a spokeswoman for the UN High Commissioner for Refugees said.

Vivian Tan said the number had jumped from an estimate of 164,000 on Thursday because the agency had found new pockets of refugees in border areas.

A UN official told AFP news agency on Friday that more than 1,000 people may already have been killed in Myanmar, mostly minority Rohingya Muslims.

"This [the refugee figures] does not necessarily reflect fresh arrivals within the past 24 hours but that we have identified more people in different areas that we were not aware of before," said Tan.

"The numbers are so alarming. It really means we have to step up our response and that the situation in Myanmar has to be addressed urgently."

Al Jazeera has been unable to independently verify the figures.