Vietnam's central belt has been deluged by torrential rains turning streets into canals, bursting riverbanks and inundating some of the country's most-visited historic sites.

Up to 1.7 metres (5 feet 6 inches) fell over one 24-hour period in a downpour breaking national records.

The fatalities occurred in Hue, Da Nang, Lam Dong and Quang Tri provinces, according to the environment ministry's disaster management agency, which said six people remained missing.

The onslaught of extreme weather is set to continue, with Typhoon Kalmaegi forecast to make landfall in the early hours of Friday morning, according to the national weather bureau.

Vietnam is prone to heavy rains between June and September, but scientific evidence has identified a pattern of human-driven climate change making extreme weather more frequent and destructive.

Ten typhoons or tropical storms usually affect Vietnam, directly or offshore, in a given year, but Typhoon Kalmaegi is set to be the 13th of 2025.

The storm is currently lashing the Philippines, where it has killed at least two people and displaced hundreds of thousands.

It could hit Vietnam's coast with winds of up to 166 kilometres per hour (100 miles per hour) as it approaches on Thursday, the national weather bureau said.

On Tuesday, the region was reeling from the past week's extreme weather -- with some remote areas still isolated by road-blocking landslides.

Nearly 80,000 houses remain flooded, according to the disaster agency, while more than 10,000 hectares (25,000 acres) of crops have been destroyed and more than 68,000 cattle killed.