Thousands of Rohingya Muslims and Bangladeshis abandoned at sea by human traffickers have nowhere to go as Malaysia turned away two boats crammed with more than 800 migrants, saying it could not afford to keep being "nice".

Indonesia and Thailand also appeared unwilling to provide refuge to desperate men, women and children, despite appeals by the UN High Commissioner for Refugees, international aid agencies and rights activists, who warned lives are at risk.

Fearing arrests, captains tied to trafficking networks have in recent days abandoned ships in the busy Malacca Strait and surrounding waters, leaving behind their human cargo, in many cases with little food or water, according to survivors.

Around 1,600 have been rescued but an estimated 6,000 remain stranded at sea.

Phil Robertson of Human Rights Watch Asia accused Indonesia, Thailand and Malaysia of playing "a three-way game of human ping pong".

Malaysian deputy home minister Wan Junaidi Jaafar said about 500 people on a boat found off the coast of northern Penang state - days after more than 1,000 refugees were taken in on nearby Langkawi island - had been given provisions and sent on their way.

"What do you expect us to do?" he said. "We have been very nice to the people who broke into our border. We have treated them humanely but they cannot be flooding our shores like this.

"We have to send the right message that they are not welcome here."

Another boat carrying about 300 migrants was turned away near Langkawi island overnight, according to two Malaysian officials.

Malaysia's Maritime Enforcement Agency director-general Mohammad Amdan Kurish said all vessels ferrying illegal immigrants will be escorted out of Malaysian waters, and patrols were being stepped up.

Malaysia, which is not a signatory of international conventions on refugees, is host to more than 150,000 refugees and asylum seekers, the majority of whom are from Burma. More than 45,000 of them are Rohingya, according to the UN refugee agency, many more than almost any other country.

Because they have no legal status, job opportunities are limited. They also have little or no access to basic services like education and health care, and are vulnerable to arrests and deportation. A small number are resettled to third countries, again because nobody wants them.

South-east Asia, which for years tried to quietly ignore the plight of Burma's 1.3 million Rohingya, finds itself caught in a spirlaling humanitarian crisis that in many ways it helped create.

In the last three years, more than 120,000 members of the Muslim minority have boarded ships to flee to other countries, according to the UN refugee agency.

But no governments in the region appear willing to take them in, fearing that accepting a few would result in an unstoppable flow of poor, uneducated migrants. At the same time, they have for years bowed to the wishes of Burma at regional conferences, avoiding all discussions of state-sponsored discrimination against the Rohingya.

Thailand's foreign minister General Thanasak Patimaprakorn said his government will not set up an official refugee shelter for the Rohingya people but is willing to provide short-term assistance based on humanitarian principles.

Denied citizenship by national law, members of the Rohingya minority are effectively stateless. They have limited access to education or adequate health care and cannot move around freely. They have been attacked by the military and chased from their homes and land by extremist Buddhist mobs.

With the crisis escalating, Thailand said it would hold an emergency meeting later this month in Bangkok to discuss the exodus and "root causes". Representatives from 15 countries are expected to attend, including Burma.

Wan Junaidi, the deputy home minister, said it was time to put pressure on the former pariah-state to address the Rohingya crisis.

"You talk about democracy, but don't treat your citizens like trash, like criminals until they need to run away to our country," he said.

Thailand reiterated this week that its policy is to help boat people, giving those who end up in their waters food, water and other provisions, before chasing them off.

Indonesia, which took 600 Rohingya and Bangaleshis on Sunday, later turned away a boat. But a foreign ministry spokesman denied it had a "push back" policy, saying the Malaysian-bound vessel strayed into its waters by accident.