Hundreds of thousands of people were desperate for food and shelter across Africa Sunday, as record floods and fresh downpours hampered relief efforts.

The continent's worst floods in three decades have deprived some 1.5 million people of their homes and subsistence in 18 countries and killed close to 300.

A Kenyan uses a canoe to cross through flood water in Budalangi.

In Uganda, one of Africa's worst-hit countries, authorities said that renewed rainfall in northeastern regions was complicating efforts to deliver aid to flood-affected areas.

"The short dry period we experienced for three days was broken yesterday and it has been raining for the past 24 hours, making all roads inaccessible," State Minister For Disaster Preparedness Musa Ecweru said.

"If the rains continue for the next four days, we do not know what will happen. The routes have been destroyed," he told AFP by phone from Soroti, the northeastern town where much of the relief effort is being coordinated.

An estimated 500,000 people are affected by the floods in Uganda. Neighbouring regions in southern Sudan, Ethiopia and Kenya have also been hit, where dozens have died as a result of the floods.

The crisis prompted Uganda's government Wednesday to declare a state of emergency, the first time President Yoweri Museveni has resorted to the measure in his 21-year tenure.

"We need air transport to deliver food items to the districts, but we are just praying that it stops raining," Ecweru said.

Forecasts predict more rain in many parts of Africa over the coming days.

West Africa has also seen its worst floods in decades, with countries such as Ghana, Togo and Nigeria paying a heavy human and economic toll.

With displaced people dying of water-borne diseases and electrocution in remote areas, casualty tolls are still being compiled across the continent.

Mali, a west African nation more often plagued by droughts, said Saturday that unprecedented rainfall had killed nine people and left more than 40,000 homeless since July.

Northern countries were not spared, with 13 people killed in Algeria, including 10 in flash floods Friday southeast of Algiers.

Aid organisations have warned that beyond the immediate needs of those displaced by the floods, destroyed crops could lead to a major food shortage in several parts of the continent.

Appeals for emergency funding have been launched by the United Nations, European Union, as well as by other governments and aid agencies.

Louis Michel, the European Commissioner for development and humanitarian aid, said Friday that the current disaster highlighted the threat posed by climate change to the world's poorest nations.

"This year's floods and droughts across much of Africa, as well as in Europe and other parts of the world, are a wake-up call," he said in a statement.

"Every new disaster highlights the danger that the world, and more particularly less developed countries and small insular states, faces from climate change," Michel added.

The torrential rains and floods that have ravaged sub-Saharan Africa are believed by some experts to be caused by the "La Nina" weather pattern, thousands of miles away in the Pacific Ocean.