Myanmar has insisted it is not barring aid workers from Rakhine State, where a counter-insurgency campaign has sparked an exodus of Muslim Rohingya refugees, but said authorities on the ground might restrict access for security reasons.
Nearly 400,000 Rohingya have fled to Bangladesh to escape a military offensive that has been described as ethnic cleansing, and raised fears of an unfolding humanitarian crisis.
"We don't block anyone," Myanmar's government spokesman Zaw Htay said.
"We don't block any organisations sending aid to those areas but they might have some difficulty travelling where access is restricted by local authorities for security reasons."
The crisis has raised questions about Buddhist-majority Myanmar's transition to civilian rule under the leadership of Nobel laureate Aung San Suu Kyi following decades of military rule.
The generals still control national security policy but, nevertheless, Suu Kyi has been widely criticised abroad for not condemning the violence. The campaign against the Muslim insurgents is popular at home.
The violence in Rakhine and the exodus of the mostly stateless Rohingya refugees is the most pressing problem Suu Kyi has faced since becoming national leader last year.
Rights monitors and fleeing Rohingya say the army and Rakhine Buddhist vigilantes have mounted a campaign of arson aimed at driving out the Muslim population.
U.N. Secretary-General Antonio Guterres has urged Myanmar to end the violence, which he said was best described as ethnic cleansing.
The rights group Amnesty International said evidence pointing to a "mass-scale scorched-earth campaign" across the north of Rakhine State was unmistakably ethnic cleansing.
"The evidence is irrefutable - the Myanmar security forces are setting northern Rakhine State ablaze in a targeted campaign to push the Rohingya people out of Myanmar. Make no mistake: this is ethnic cleansing," said Tirana Hassan, the group's crisis response director.
The group said it had detected 80 big fires in Rohingya areas since August 25, and while the extent of damage could not be verified, due to access restrictions by the government, "they are likely to have burned down whole villages".
It said it also had credible reports of Rohingya militants burning the homes of ethnic Rakhine and other minorities. About 30,000 non-Muslims have also been displaced.
