A tourist boat carrying as many as 53 people has capsized in stormy weather, sparking a major rescue operation.

Rescuers have recovered at least 27 bodies from Vietnam's Halong Bay after the cruise vessel tipped over.

Some 48 tourists and five members of crew were believed to be on board when immense waves, strengthened by strong winds and heavy rain, caused the boat to lose its centre of balance.

Eight children are understood to be among the recovered bodies.

At time of writing, the nationalities of those involved is not yet known and emergency crews are understood to be continuing their search for survivors.

According to local press, the tourists on board included families with children, and were from the capital, Hanoi.

Rescuers have located 11 of the tourists alive as of 8:30pm local time today.

Two rescue craft and a number of smaller local vessels are understood to be working at the scene in a joint operation between police, navy, border guards. and port authorities.