Vietnam's central belt has been deluged by torrential rain 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 an update from the environment ministry's disaster management agency, which said six people remained missing.

On Sunday the toll had stood at 35.

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

"It's exhausting," said Tran Thi Ky from the city of Hoi An, where the UNESCO world heritage site of the ancient town was drenched in muddy waist-high water.

"We are tired of floodings, but what can we do," the 57-year-old told AFP, after her home was flooded three times in less than 10 days.

"We brought all our furniture to high ground but they are all wet anyway."

Vietnam is prone to heavy rain 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 central Philippines, where it has killed at least five people and displaced hundreds of thousands.

It could hit Vietnam's coast with winds of up to 166 kilometres (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 landslides that blocked roads.

State media reported approximately 15 metres of the wall at the Hue Imperial Citadel, known as the Dai Noi, had collapsed.

Nearly 80,000 houses are 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.