Up to 8,000 Rohingya and Bangladeshi migrants are thought to be stranded at sea as Indonesia and other south Asian governments prevent them from coming ashore.
One boat carrying nearly 800 people has been rescued off the coast of Indonesia, but other vessels have been set back to sea.
The Indonesian government has cracked down on migrants coming to the country and is preventing boats from entering its waters, despite calls from the UN to rescue those adrift.
One boat carrying hundreds of migrants has already been turned back by the Indonesian navy while another, from Thailand, has been left adrift in the Andaman sea, struggling to land.
Malaysia, too, has said it would push migrant boats back to sea.
The UN has warned the situation could develop into a “massive humanitarian disaster”, and Human Rights Watch has warned of deadly “human ping-pong” between countries as a growing number of nations reject migrant boats.
— United Nations (@UN) May 15, 2015
UN spokesman Stephane Dujarric said: “The secretary-general urges governments to ensure that the obligation of rescue at sea is upheld and the prohibition on refoulement [the expulsion of refugees] is maintained”.
An estimated 2,500 migrants have landed on Indonesia’s western tip and the north west coast of Malaysia in the last week alone. However, those turned away are now left to drift on the own, with dwindling food and water supplies.
They are part of a new wave of Asian “boat people”, many of whom have been abandoned by smugglers following a crackdown on human trafficking in Thailand.
Thailand is a common destination for those escaping Myanmar’s Rakhine state, which heavily discriminates against its Rohingya Muslim minority group.
Many of those are thought to be heading to Muslim Malaysia through Thailand. However, Thailand’s Prime Minister Prayuth Chan-o-cha warned that Rohingya migrants could steal jobs from Thai people.
“Right now we have to find a place for them to stay. In the future, if many more of them come, it will cause a problem. They will steal the jobs and livelihoods of Thais.”
The UN believes that the pattern of migration across the Bay of Bengal will not stop until Myanmar ends discrimination.
“Until the Myanmar government addresses the institutional discrimination against the Rohingya population, including equal access to citizenship, this precarious migration will continue,” UN human rights chief Zeid Ra’ad Al Hussein said.
Channel 4 News Asia correspondent John Sparks said both activists and governments are clashing over the migrant crisis.
“The Thais say their policy is to provide food and humanitarian assistance and encourage the boats to continue ‘to their final destination’. The result, say activists and inter-governmental groups, is a game of ‘ping-pong’ that could have catastrophic results. “
The migrant crisis in Asia reflects a similar situation in Europe, where a growing number of migrants are seeking refuge in Britain and other European countries. Last month 900 people were feared dead after a migrant boat capsized in the Mediterranean.