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.