The wooden boat was touring in the Unesco World Heritage Site, in Quang Ninh province, when it went down.

Fifteen people, including nine foreigners, have been rescued.

It is not yet clear why the boat sank, although a local government official said initial information suggested part of the boat had broken without warning.

Halong Bay, renowned for its hundreds of tiny islands and freshwater swamp forests, is one of Vietnam's most popular tourist destinations.

 The boat, reported to be a traditional junk on which people were staying overnight, went down before dawn near Titov island.

Those rescued reported seeing a wooden plank tear away from the boat, followed by a gush of water that overwhelmed it, pulling the vessel down, local government official Vu Van Thin said.

"Crew members tried to stop the water from coming in and alerted the tourists who were sleeping, but the water came in and the boat sank quickly. All of the 12 people who died were in the cabins," he was quoted by the Associated Press as saying.

The bodies were sent to a nearby hospital for formal identification.

The victims were later identified as holidaymakers from the US, Britain, Australia, Japan, Russia, France, Sweden and Switzerland, along with a Vietnamese tour guide.

Those who survived - nine foreigners and six locals - were able to jump into the water, from where they were pulled to safety by people on other tour boats anchored close by.

Our First Choice Safety Notice

Regarding the boat acident of Truong Hai Company (Backpacker's Tour) in Halong Bay on 17 Feb. 2011, we would like to update you safety information of our boats to ensure your confidence of Halong Bay's trip:

1. All of our boats have life vests in each cabin (1 per guest) and at public area, life buoys, life rafts that enough for maximum guests and crew on board . Each boat is with tender for rescue and there are life vests on tender as well.

2. All of our boats are under professional daily technical supervision and yearly thorough maintenance. All guests are briefed and given safety procedures on board with clear instruction in case of emergency. The crews are trained with clear written procedures how to deal with emergency

3. All boats are invested with professional marine safety equipments: VHF, GPS, radar, walkie talkies, water licking alarm system, prevent drowning water pump system, fire alarm & fire extinguished system

4. All boats are well checked by local marine registration authority yearly after 01 month maintenance on dry dock/each boat. See the maintenance period of Ginger (1st May to 31st May 2011 ), Jasmine Cruise (1st July to 31st July 2011), Violet Cruise (13th September to 30th September 2011)

5. All boats are covered with maximum boat insurance (maximum boat value) and maximum passenger & crew insurance (local insurance company, 50 million VND/case)

Safety is our top priority. Please let us know if you need any further information.