The United Nations urged Myanmar leader Aung San Suu Kyi on Thursday to visit the country's divided northwest to reassure civilians they will be protected amid accusations that soldiers have raped Rohingya Muslim women, burnt houses and killed civilians.

Myanmar's military and government have rejected the allegations. Soldiers have poured into the area along Myanmar's frontier with Bangladesh, responding to coordinated attacks on three border posts on October 9 that killed nine police officers.

Suu Kyi last Friday accused "the international community" of stoking resentment between Buddhists and Muslims in the Myanmar's northwest.

"The refusal by the Myanmar authorities to take a strong stance against hardliners, and the adoption of a generally defensive rather than proactive approach to providing security to the local population, have caused frustration locally and disappointment internationally," Vijay Nambiar, special advisor to UN Secretary-General Ban Ki-moon, said in a statement.

"Only by responding concretely to these concerns will the government be able to resolve the crisis and preserve its international standing," said Nambiar, appealing to Suu Kyi to visit Maungdaw and Buthidaung in Rakhine State.

The army crackdown in Rakhine State has killed at least 86 people and sent 10,000 fleeing over the border to Bangladesh. The crisis poses a challenge to Nobel Peace Prize winner Suu Kyi, who swept to power last year on promises of reconciliation.

Former U.N. chief Kofi Annan on Tuesday urged Myanmar security forces to act within the rule of law.