Malawi has declared a state of disaster with more than 200 people confirmed dead after Cyclone Freddy ripped through southern Africa for a second time, triggering floods and landslides.

The record-breaking storm caused most deaths in Malawi's commercial hub, Blantyre, where dozens of children were among those who perished in mudslides.

Authorities in Malawi said at least 190 people were killed with 584 injured and 37 missing, while the government of neighbouring Mozambique reported 20 deaths and 24 injured.

Toll to rise

Rescue workers warned that more victims were likely as they scoured destroyed neighbourhoods for survivors.

"The situation is very dire," said Guilherme Botelho, emergency project coordinator for Doctors Without Borders in Malawi.

Aid agencies fear that the flood contamination of drinking water will exacerbate a cholera outbreak in Malawi, where at least 19,000 people have been displaced.

Over the weekend Cyclone Freddy made landfall for the second time since late February after brewing off Australia and crossing the Indian Ocean.

Conditions were expected to ease from Wednesday evening.