Mozambique's President Filipe Nyusi says more than 1000 may have by killed by Cyclone Idai, which many say is the worst to hit the area in more than 20 years.
Speaking to state Radio Mozambique, Nyusi says that although the official death count is currently 84, he believes the toll will be more than 1000.
"It appears that we can register more than 1000 deaths," he said on Monday, adding that more than 100,000 people are at risk.
"The waters of the Pungue and Buzi rivers overflowed, making whole villages disappear and isolating communities, and bodies are floating," Nyusi said.
"It is a real disaster of great proportions."
Nyusi spoke after flying by helicopter over the central port city of Beira and the rural Manica and Sofala provinces in which he saw widespread flooding and devastation.
Other officials in emergency services cautioned that while they expect the death toll to rise significantly, they have no way of knowing if it will reach the president's estimate of 1000.
The Red Cross said that 90 per cent of Beira, a city of 500,000, had been damaged or destroyed.
Beira has been severely battered by the cyclone which cut off electricity, forced the airport to shut down and cut off road access to the rest of the country. Cyclone Idai first hit Beira last week and then moved inland to Zimbabwe and Malawi.
Beira has been severely battered by the cyclone which cut off electricity, forced the airport to shut down and closed road access to the city, the International Federation of Red Cross and Red Crescent Societies said on Monday.
Cyclone Idai first hit Beira last week and then moved inland, spreading heavy winds and rainfall to Zimbabwe and Malawi.
More than 215 people have been killed by the storm, according to official figures in the three countries.
Hundreds more are missing and more than 1.5 million people have been affected, according to the Red Cross and government officials.
Jamie LeSueur, who led a Red Cross aerial assessment of the city, said the scale of the damage to Beira is "massive and horrifying"
"The situation is terrible. The scale of devastation is enormous. It seems that 90 per cent of the area is completely destroyed," LeSueur said.
At least 126 people had died in Mozambique and Malawi, according to the Red Cross. In Zimbabwe, 89 people have died from the floods, the country's information ministry said on Monday.
Nyusi and Zimbabwean President Emmerson Mnangagwa both returned from foreign trips to attend to the emergencies.