HANOI (AFP) - United Nations chief Ban Ki Moon said on Saturday that saving the lives of migrants stranded at sea in South-east Asia should be a "top priority" as the region battles with an exodus of boat people fleeing persecution and poverty.

The UN Secretary-General said he hoped regional nations would tackle the "root causes" of the current exodus at an upcoming conference in Thailand later this month.

"But when people are drifting on the sea, how we can search and rescue them and provide life saving humanitarian assistance, that is a top priority at this time," he told reporters during a visit to Hanoi.

Mr Ban said he had been in recent discussions with regional leaders in Thailand, Malaysia and Myanmar and urged a "very clear addressing of the root causes of this issue, why people are fleeing".

His comments come as Myanmar faces growing international pressure to address its treatment of the country's 1.3 million Rohingya minority Muslims.

The widespread persecution of the impoverished community in western Rakhine state is one of the primary causes for the current regional exodus, alongside growing numbers trying to escape poverty in neighbouring Bangladesh.

Most migrants aim for Malaysia and Indonesia through dangerous and lucrative smuggling networks that criss-cross the region.

Ban also called on countries who receive migrants "not to send them back to a dangerous circumstance or situation".

Thailand has organised a regional conference in Bangkok on May 29 to address the crisis.