A boy survived the sinking of a tourist boat in Vietnam which killed dozens of people by sheltering in an air pocket of the overturned vessel, it has emerged.

The death toll from a tourist boat accident in Vietnam's Halong Bay climbed to at least 38 with several people still missing, the government said, as rescuers continued to search for survivors while bracing for the approach of Typhoon Wipha.

The boat, carrying 48 passengers and five crew members, was on a sightseeing tour of Ha Long Bay when a sudden storm caused it to overturn, state media said. At least 10 people were rescued.