Myanmar's national leader Aung San Suu Kyi will not attend the upcoming UN General Assembly session in New York.

A spokesperson for her party, the National League for Democracy (NLD), told Reuters news agency late on Tuesday that the Nobel Peace Prize winner had withdrawn from the meeting in New York on September 20.

No reason was provided for her withdrawal.

Aung San Suu Kyi, whose official title is state counsellor, faces mounting criticism over the systematic killings and displacements of the Muslim-majority ethnic Rohingya in the western Rakhine State.

Since August 25, 370,000 Rohingya have fled to Bangladesh. But a spokesperson for the NLD said she was not aware of the reason for the Aung San Suu Kyi's withdrawal from this year's General Assembly.

READ MORE: UN Security Council to discuss Rohingya situation

"She's never afraid of facing criticism or confronting problems. Perhaps she's got more pressing matters here to deal with," Aung Shin, the spokesman, told Reuters.

U Henry Van Thio, Myanmar's vice president, is expected to attend the assembly instead, and speak on behalf of Myanmar, China's official Xinhua news agency reported on Wednesday.

The crisis over the security forces' fierce response to Rohingya is the biggest problem Aung San Suu Kyi has faced since becoming Myanmar's leader last year.

Critics have called for her to be stripped of her Nobel Peace Prize for failing to do more to address the crisis.

Growing pressure

In her first address to the General Assembly as national leader in September last year, Aung San Suu Kyi defended her government's efforts to resolve the crisis over treatment of the Muslim minority.

International pressure has been growing on Myanmar to end the violence in the western Rakhine State that began on August 25 when a ragtag Rohingya militia attacked about 30 police posts and an army camp.

The attacks prompted a sweeping military counteroffensive that refugees say is aimed at pushing Rohingya out of Myanmar.

Reports from refugees and rights groups paint a picture of widespread attacks on Rohingya villages in the north of Rakhine by the security forces and ethnic Rakhine Buddhists, who have put numerous Muslim villages to the torch.

But Myanmar authorities have denied that the security forces, or Buddhist civilians, have been setting the fires, instead blaming the Rohingya militia. Nearly 30,000 Buddhist villagers have also been displaced, they say.

The Trump administration has called for protection of civilians, and Bangladesh says all of the refugees will have to go home and it has called for safe zones to be created in Myanmar to enable them to do so.

But China, which competes with the US for influence in the region, said on Tuesday it backed Myanmar's efforts to safeguard "development and stability".

Full control

The military, which ruled for almost 50 years until it began a transition to democracy in 2011, retains important political powers and is in full control of security.

The UN Security Council is to meet on Wednesday behind closed doors for the second time since the latest crisis erupted.

Matthew Rycroft, Britain's ambassador to the UN, said he hoped there would be a public statement agreed by the council.

However, rights groups criticised the 15-member council for not holding a public meeting.

Diplomats have said China and Russia would probably object to such a move and protect Myanmar if there was any push for council action to try and end the crisis.