Myanmar's leader Aung San Suu Kyi will address the crisis engulfing Rakhine state next week, in her first speech since scores were killed in violence that has sent nearly 380,000 Rohingya Muslims fleeing to Bangladesh and sullied her reputation as a defender of the oppressed.

A crackdown by Myanmar's army, launched in response to attacks by Rohingya militants on August 25, has pushed vast numbers of refugees from the stateless Muslim minority across the border.

The violence has incubated a humanitarian crisis on both sides of the border and put intense global pressure on Suu Kyi to condemn the army campaign, which the UN has described as having all the hallmarks of "ethnic cleansing".

At a press conference late Wednesday government spokesman Zaw Htay said Suu Kyi would "speak for national reconciliation and peace" in a televised address on September 19.

He said the Nobel laureate, who has been pilloried by rights groups for failing to speak up for the Rohingya minority, would skip the United Nations General Assembly next week to tackle the crisis unfurling at home.

She was needed in Myanmar to "manage humanitarian assistance" and "security concerns" caused by the violence. Competing rumours have intensified anti-Muslim rhetoric across the Buddhist-majority country.

Suu Kyi has been condemned for a lack of moral leadership and compassion in the face of a crisis that has shocked the international community.

Her limited comments so far have referenced a "huge iceberg of misinformation" and played down alleged atrocities against the Rohingya.

Bangladesh is struggling to provide relief for exhausted and hungry refugees -- some 60 percent of whom are children -- while nearly 30,000 ethnic Rakhine Buddhists as well as Hindus have also been displaced inside Myanmar.

Nine thousand more Rohingya refugees poured into Bangladesh on Wednesday, the UN said, as authorities worked to build a new camp for tens of thousands of arrivals who have no shelter.

Suu Kyi, Myanmar's first civilian leader in decades, has no control over the powerful military, which ran the country for 50 years. A free election was finally held in 2015.

There is also scant sympathy among Myanmar's Buddhist majority for the Rohingya, who are branded "Bengalis" -- shorthand for illegal immigrants.

But outside of her country Suu Kyi's reputation as a defender of the oppressed is in ruins.

Rohingya refugees have told chilling accounts of soldiers firing on civilians and razing entire villages in the north of Rakhine state with the help of Buddhist mobs.

The army denies the allegations.

The UN Security Council was scheduled later Wednesday to discuss the refugee crisis in a closed-door meeting, with China expected to block any attempts to censure its Southeast Asian ally.

Ahead of the meeting twelve Nobel Laureates signed an open letter urging the Security Council to "intervene immediately by using all available means" to end the tragedy and "crimes against humanity" unfolding in Rakhine.

Fallen star

Suu Kyi, a Nobel Peace Prize winner garlanded for her dignified and defiant democracy activism under Myanmar's former junta, was once the darling of the international community.

She made her debut before the UN assembly last September, winning warm applause for a speech delivered months after she became Myanmar's first civilian leader.

In it she vowed to find a solution to long-running ethnic and religious hatred in Rakhine "that will lead to peace, stability and development for all communities within the state".

In a sign of how far her star has fallen, the same rights groups that campaigned for her release from house arrest have blasted her for failing to speak up in defence of the Rohingya.

Sympathisers say her hands are tied by the army, which still runs parts of the government and has complete control over all security matters.

While the US and other Western powers -- as well as the Muslim world -- have criticised the military campaign, Beijing on Tuesday offered Myanmar support -- saying the country was entitled to "safeguard" its stability.

Human Rights Watch's Phil Robertson urged the Security Council to pass a "global arms embargo" on Myanmar's military but said he expected China to to water down any moves.

The 1.1-million strong Rohingya have suffered years of discrimination in Myanmar, where they are denied citizenship even though many have long-lasting roots in the country.

Bangladesh does not want the group either, though it is providing the refugees with temporary shelter.

Many Rohingya have died making the perilous journey across the border, with nearly 100 drowning in boat trips across the Naf river that divides the two countries.

Bangladeshi authorities want to establish a 2,000-acre camp close to Myanmar's border to house around 250,000 Rohingya and are also planning to build facilities on a flood-prone island.