The death toll from the sinking of a boat carrying members of Myanmar's persecuted Rohingya Muslim minority climbed to 27 on Tuesday, as a survivor recalled a harrowing journey that left him floating for days in the Andaman Sea.

"I saw one person die. They drowned," Iman Sharif told reporters shortly after he was rescued on Tuesday and taken into custody by Malaysian authorities.

Iman said he was aboard a large boat for eight days before being transferred to a smaller one with around 70 people. But the vessel sank shortly after, and he clung on to wreckage for days before washing up on a Malaysian island.