More than 200 people are now confirmed dead in Malawi after Tropical Storm Freddy ripped through southern Africa for the second time in a month, reports BBC.
Huge amounts of brown water have cascaded through neighbourhoods, sweeping away homes.
Malawi's commercial hub, Blantyre, has recorded most of the deaths, including dozens of children.
Aid agencies are warning that the devastation will exacerbate a cholera outbreak in Malawi.
The government has declared a state of disaster in 10 southern districts that have been hardest-hit by the storm.
Rescue workers are overwhelmed, and are using shovels to try to find survivors buried in mud.
"We have rivers overflowing, we have people being carried away by running waters, we have buildings collapsing," police spokesman Peter Kalaya told the BBC.
Recalling how he helped rescue a child, Blantyre resident Aaron Ntambo said: "The child was stuck up to her head in the mud. She was crying for help. Even though the water was very strong, we managed to cross and rescue her. It was very difficult but we managed to pull her out."
Officials at the main referral hospital in the city said they could not cope with the sheer number of bodies that they were receiving.
Medical charity Doctors Without Borders said that more than 40 children were pronounced dead on arrival at the hospital.
Officials appealed to bereaved families to collect the corpses for burial as the hospital's mortuary was running out of space.
The government's disaster relief agency said more than 20,000 people have been displaced.
The death toll is expected to rise as some areas remain cut off because of relentless rain and fierce winds.
The storm has also crippled Malawi's power supply, with most parts of the country experiencing prolonged blackouts.
The national electricity company said it was unable to get its hydro-power plant working as it had been filled with debris.
Densely-populated poorer communities, living in brick and mud houses, have been hardest-hit.
Some of these houses have crumbled into flood waters, while others have been entirely swept away.
The collapse of roads and bridges had hampered rescue operations, while helicopters could not be used either because of the heavy rains and strong winds.
The government has appealed for help for the tens of thousands of people who have been left without food and shelter.
Freddy is the strongest tropical cyclone on record and could also be the longest-lasting one, according to the World Meteorological Organization.
On Sunday the storm struck Mozambique as a cyclone - for the second time in a less than a month - after battering the island nation of Madagascar in the Indian Ocean, causing severe destruction.
It has been difficult to determine the extent of the damage caused in Mozambique and the number of deaths, as power supply and phone signals were cut off in some parts of the affected areas.
About 20 deaths have so far been reported.
Experts says climate change is making tropical storms around the world wetter, windier and more intense.
Freddy had broken records for the strength it accumulated over the 8,000-km (5,000-mile) path it travelled across the Indian Ocean from north-western Australia.