Bangkok: Malaysia's former prime minister Mahathir Mohamad has joined a growing number of international figures criticising Myanmar's opposition leader Aung San Suu Kyi for failing to speak out against the persecution of Rohingyas.

In a speech to a conference on the plight of the Rohingyas at the Nobel Institute in Norway -  which awarded Ms Suu Kyi its peace prize in 1991 for her stand against Myanmar's brutal military regime - Dr Mahathir said she should realise that oppression by Myanmar's government is intolerable.

Dr Mahathir joined US philanthropist George Soros and Nobel laureates Desmond Tutu, Mairead Maguire and Jose Ramos-Horta at the two-day Oslo Conference on Myanmar's Systematic Persecution of Rohingyas on May 26 and 27.

"And yet few people from Myanmar have risen to the occasion to defend the rights of Rohingyas who, after all, are citizens of Myanmar," Dr Mahathir said.

Myanmar's military-dominated government regards the 1.3 million Rohingyas living in western Arakan state as illegal migrants from Bangladesh and refuses them citizenship despite their having lived there for centuries.

Ms Suu Kyi was pointedly not invited to the Norway conference.

Archbishop Tutu told the conference via video link that the plight of Rohingyas was "one of the most enduring human rights crises on Earth".

"As lovers of peace and believers in the right of all members of the family to dignity and security, we have particular responsibilities to the Rohingya," he said.

The Dalai Lama, human rights and refugee groups have called on Ms Suu Kyi to speak up for Rohingyas as a humanitarian crisis involving thousands of people fleeing Myanmar has unfolded across the Bay of Bengal, where thousands of people are believed be adrift at sea.

More than 2500 migrants could still be stranded on boats, according to estimates by the United Nations.

The UNHCR, the UN's refugee agency, cautioned that its figures for those still risking sickness and starvation at sea were loose estimates.

"What we know is the arrivals, especially in Indonesia where we have full access, and in Thailand, where we have access," said Vivian Tan, a spokeswoman for the UNHCR in Bangkok.

"In Malaysia the figures are from the government and in Myanmar we have an estimate. What we're not sure about are those who are still at sea. This is a combination of media reports, survivor accounts and any other local resources."

The UN and the US have said the deadly pattern of migration across the Bay of Bengal will continue unless Myanmar ends discrimination against the mostly Muslim Rohingyas.

Ms Suu Kyi bristles when asked why she has failed to denounce religious bigotry in Myanmar.

"Those who criticise me for not condemning one side or the other - they've never said exactly what they hope will come out of such condemnation," she was quoted as saying last month. "You're just taking the moral high ground for the sake of sounding good - it sounds a little irresponsible."

International outrage over the discovery of mass graves and prison camps of people from Myanmar and Bangladesh and the abandonment of thousands of others on the open sea after a crackdown on human trafficking networks in Thailand and Malaysia has caused a backlash in Myanmar, where Buddhists fear the Muslim world's backing of the Rohingyas.

About 300 people, led by about 30 Buddhist monks, shouted slogans against the United Nations and Western media during a protest march in Yangon on Wednesday. Protesters carried banners calling the migrants and asylum seekers "terrorists" and "beasts".

A 17-nation meeting to discuss the Rohingya crisis will be held in Bangkok on Friday.

with Reuters