Survivors of a boat that made it to Indonesia after months at sea have spoken of violence and killing on board the vessel.
One woman said she had witnessed horrific violence, even on children.
"We didn’t have food for two weeks," she told BBC. "We were starving. I saw small, innocent children slaughtered at sea."
Another man said the violence on board the ship was brutal, and up to 100 people were killed.
Some people were hacked to death. Others were beaten,” he said. “I saw people being thrown overboard.
"I could see their bodies sinking in the sea.”
The migrants thought they were fleeing Myanmar and Bangladesh for a better life. They wanted to reach Malaysia but their boat wasn’t allowed to land.
Some may be sent home and others may be given asylum. But for the many more on boats at sea, their fates remain unknown.
Abbott's stance
Meanwhile Australian Prime Minister Tony Abbott said he won't criticise countries that are turning back asylum-seeker boats to stop people smuggling.
Mr Abbott said on Sunday he was not critical of efforts made by other nations to stop people smuggling in the region.
"I don't apologise in any way for the action that Australia has taken to preserve safety at sea by turning boats around where necessary," he said.
"And if other countries choose to do that, frankly that is almost certainly absolutely necessary if the scourge of people smuggling is to be beaten."
If that meant taking "more vigorous" action on the high seas or closer to Burma, so be it, he said.
Thai clampdown
An estimated 25,000 Bangladeshis and Rohingya boarded smugglers' boats in the first three months of this year, twice as many as in the same period of 2014, the UNHCR has said.
A clampdown by Thailand's military junta has made a well-trodden trafficking route into Malaysia - one of Southeast Asia's wealthiest economies - too risky for criminals who prey on Rohingya fleeing persecution in Buddhist-majority Myanmar and on impoverished Bangladeshis looking for work.
In response, many people-smugglers appear to have abandoned their boats in the Andaman Sea, leaving thousands thirsty, hungry and sick, and without fuel for their vessels' engines.
One of those boats was towed away from the Thai coast by Thailand's navy on Saturday, only to be intercepted off the Malaysian coast.
Reuters journalist on a speedboat taken from southern Thailand's coast said that the people aboard had little shelter from the blazing sun. Some of the women were crying, and some passengers waved their arms and shouted.
The International Organization for Migration has criticised Southeast Asian governments for playing "maritime ping-pong" with the migrants and endangering their lives.
US Secretary of State John Kerry on Friday urged Thailand to considering sheltering the homeless Rohingya and called on its neighbours not to send the migrants back out to sea.
Responding to the pressure, Malaysian Prime Minister Najib Razak said his country already had 120,000 illegal migrants from Myanmar and the "humanitarian catastrophe" was a global issue to be resolved by the international community.
"We allow some of them to land and provide humanitarian aid to them but Malaysia must not be burdened with this problem as there are thousands more waiting to flee from their region," Najib told the state news agency Bernama on Saturday.
Myanmar defiant
The United Nations said this week that the deadly pattern of migration across the Bay of Bengal would continue unless Myanmar ended discrimination.
Most of Myanmar's 1.1 million Rohingya Muslims are stateless and live in apartheid-like conditions. Almost 140,000 were displaced in clashes with ethnic Rakhine Buddhists in 2012.
Myanmar terms the Rohingya "Bengalis", a name most Rohingya reject because it implies they are immigrants from neighbouring Bangladesh despite having lived in Myanmar for generations.
Thailand is hosting talks on May 29 for 15 countries to discuss the crisis.
Myanmar had not received an invitation to the meeting and would not attend if the word Rohingya was used, Zaw Htay, a senior official from the president's office, said on Saturday.
"We haven't received any formal invitation from Thailand officially yet," he said in an emailed response to questions.
"And another thing, if they use the term 'Rohingya' we won't take part in it since we don't recognise this term. The Myanmar government has been protesting against the use of it all along."
In a routine note to Congress, US President Barack Obama said the United States, while not curtailing engagement with Myanmar as it introduces democratic reforms after decades of military rule, would maintain some sanctions on the country.
White House spokesman Eric Schultz said on Friday that Washington continued to raise its concerns with Myanmar over the migrants "because of dire humanitarian and economic situations they face at home out of fear of ethnic and religious violence."
With AAP, Reuters.
