Niger has borne the brunt of almost four weeks of heavy rains, with almost 16,000 people affected, said Elisabeth Byrs, spokeswoman for the UN Office for the Coordination of Humanitarian Affairs.

To the west, in Burkina Faso, the figure is about 6,000.

Besides destroying homes, the floods have also wiped out swathes of farmland and devastated herds of livestock, raising the spectre of hunger for a population that has long been vulnerable to food shortages.

There are also rising fears that the disaster could fuel deadly outbreaks of cholera and malaria.

Aid agencies are rushing supplies to the affected areas, including tents, food, medicines and mosquito nets, said Byrs.

The floods have also affected other West African nations, including Mauritania, Mali and Nigeria.