Tropical storm Ana has killed at least 34 people in Madagascar and two people in Mozambique in recent days while knocking out power in Malawi, authorities in the three countries said on Tuesday.
The storm, which formed over the east coast of Africa's largest island Madagascar, has brought heavy rains causing flooding and mudslides that have swept away houses in the capital Antananarivo.
The latest report from Madagascar's disaster management agency on Tuesday showed that 34 people have died and nearly 65 000 were left homeless since last week.
Across the Indian Ocean, the storm made landfall on mainland Africa on Monday, bringing heavy rains in Mozambique's central and northern districts.
Mozambique's National Institute for Disaster Risk Management on Tuesday said two people were killed, with 49 others injured in Zambezia province.
The UN forecasts the storm will cause widespread flooding, uproot people and inflict infrastructural damages.
The storm will potentially affect "highly vulnerable populations who have already suffered from previous natural disasters and conflict in northern Mozambique", the United Nations Office for the Coordination of Humanitarian Affairs (OCHA) said in an update.
Government and UN agencies estimate that 500 000 people may be impacted in Mozambique's Nampula, Zambezia, and Sofala provinces.
In neighbouring Malawi, the storm plunged most parts of the country into darkness overnight Monday after flash floods raised the water levels, forcing the electricity generation company to shut down its power generating machines.
"Our generation depends on water levels and currently the levels are too high for us to run the machines. It is too risky," Moses Gwaza, spokesperson for the power utility Electricity Generation Company, told AFP.
In an update on Tuesday morning, the electricity generation company said it was starting to restore power generation.