More than half a million people have seen their homes or livelihoods affected by the rising waters [Reuters]

The death toll from weeks of severe flooding in Vietnam has climbed to 100, the government has said, as a fresh deluge in central provinces prompted the evacuation of about 30,000 people.

The latest victims, 17 adults and five children, were killed when floods triggered by torrential rain swamped four central provinces in recent days, the national flood and storm control committee said on Wednesday.

Flooding in the country's southern Mekong Delta had already left 78 people dead.

The UN said on Monday that 65 children under the age of 16 were among those killed in the delta region, most of them due to drowning.

As the floods battered parts of central Vietnam, newspapers ran pictures of inundated houses and streets in the town of Hoi An and the ancient city of Hue. Both are UNESCO World Heritage Sites.

Nationwide, more than half a million people have seen their homes or livelihoods affected by the rising waters, which have hit around 140,000 homes.

Unusually heavy monsoon rains have caused devastation across the wider region, with more than 500 dead in Thailand's worst flooding in half a century and around 250 killed in Cambodia.

Forecasters say more rain is expected in the region.