The death toll from a new round of torrential rain, flooding and landslides in central Vietnam since the weekend has risen to 16, local authorities said on Thursday, with water levels rising further in already inundated towns and villages.

Rainfall exceeded 1,500 millimetres in several parts of central Vietnam over the past three days. The region is home to a key coffee production belt as well as the country's most popular beaches, but it is highly prone to storms and floods.

Business owner Bui Quoc Vinh, 45, said he was safe in his 24th-floor apartment in Nha Trang but his restaurants and shops on the ground floor were under about a metre of water. His employees were even worse off.

"I am worried about our furniture in my restaurants and shops, but of course I cannot do anything now," he said

"My staff have to take care of their flooded homes," which he said were under two metres of water. "I don't think the water is going to recede soon as the rain has not stopped."

Photographs shared on state media reports show residents, including children, sitting on the roofs of flooded houses and calling for help via social media platforms.

"Any group out there please help! We've been sitting on the roof since 10pm last night, including kids and adults," a resident of Khanh Hoa province posted on a local Facebook page.

At least 16 people have been killed since the weekend, while the search was continuing for five others, the environment ministry said.

More than 43,000 houses were submerged, while several major roads remained blocked due to landslides.

Deputy Prime Minister Ho Quoc Dung told the leaders of three flood-affected provinces, Khanh Hoa, Dak Lak and Gia Lai, to mobilise army, police and other security forces to "promptly relocate and evacuate people" to safe areas.

Natural disasters have left 279 people dead or missing in Vietnam and caused more than US$2 billion in damage between January and October, according to the national statistics office. (AFP, Reuters)