The disaster prompted the Zambian government to ask for US$13 million in Western aid. Zambian state television broadcast images of refugees carrying beds, chickens and goats over their heads as they moved through the surging floodwaters.

Half of the southern African country has been put on alert.

"I have lost everything that I owned and my children cannot go to school because the roads have been destroyed and the bridge we normally cross to get to other places has been damaged too," one villager said.

Tens of thousands are at risk after torrential rains inundated the region, said the United Nations, which was consulting governments to assess the flood damage.

Authorities in Zambia and Zimbabwe said there had been casualties but did not provide details.

Raging waters in Zimbabwe, suffering from an economic crisis marked by years of food and fuel shortages, have cut road links.

FOOD SHORTAGE FEARS

Heavy downpours are common in southern Africa during the annual rainy season, which runs generally from November to April, but the relentless rain is unusual.

Fields are waterlogged and crops have been damaged, raising fears of a return to the food shortages that plagued the region as little as three years ago.

Officials in Zambia said 500 houses collapsed in Monze, 200 km (125 miles) south of the capital Lusaka, while others were trapped on an island due to the rising waters.

Zambia's government is distributing tents and food to people in its southern region, while the Red Cross is providing chlorine to purify drinking water and avert outbreaks of deadly diseases such as cholera, which causes severe dehydration.

"Our main worry is that diseases such as cholera and malaria will come in to make the situation worse as we get more floods," Austin Sichinga, who is overseeing Zambia's disaster management efforts, told a press conference in Lusaka.

Sichinga said the numbers of Zambians affected by the disaster could rise beyond the 1.5 million mark, especially if forecasts for more rain proved accurate.

In Mozambique, floods threatened to expose children to diseases such as diarrhoea, Save the Children said. Diarrhoea is one of the biggest killers of children in Africa.

"Several rivers in Mozambique have reached dangerously high levels, forcing thousands of children from their homes in order to seek safety on higher ground," the humanitarian group said.

"As the waters rise and the threat of flooding intensifies it is predicted that up to 250,000 people, around half of them children, could be affected," it said in a statement.

Floods killed 45 people and left 285,000 homeless last year after torrential rain and hurricanes swept through Mozambique.