AFP/ Langkawi

Malaysia has turned away two vessels carrying a combined 600 migrants, an official who spoke on condition of anonymity said Thursday, as concern mounted in the region over the fate of boatloads of people stranded at sea.

The boats were intercepted off the northern Malaysian islands of Penang and Langkawi and told they could not land.

"Last night, one boat was pushed back after it entered Malaysian waters off Penang and one more boat was prevented from entering Langkawi waters," the official said.

The boat off Penang was given bottled water before it was sent away.

Malaysia and Indonesia have vowed to bar boats bearing desperate migrants from Myanmar and Bangladesh after nearly 2,000 boat people were rescued or swum to shore earlier this week.

The UN refugee agency and rights groups have expressed outrage over the policy, saying thousands of men, women and children are believed stuck out at sea in deplorable conditions after a Thai police crackdown disrupted well-worn people-smuggling routes.

They warn that repelling such boats could seal the doom of impoverished passengers already at risk of starvation and disease after long weeks at sea.

Some of the recent arrivals, who have spent up to three months on overcrowded vessels, have reported that many of their fellow passengers had died on the harsh ocean passage, their bodies thrown overboard.

Regional governments have faced mounting calls to urgently launch search and rescue operations rather than driving off boats, and to come up with a coordinated strategy for handling the migrant influx.

Thailand has called a May 29 regional meeting on the issue.