Emergency officials in Mozambique have cautioned that while they expect the death toll to rise significantly, they have no way of knowing how high the death toll will be.
More than 1 000 people were feared dead in Mozambique four days after a cyclone slammed into the country, submerging entire villages and leaving bodies floating in the floodwaters, the nation's president said.
"It is a real disaster of great proportions," President Filipe Nyusi said.
WATCH: More than 120 people die after cyclone hits Mozambique, Zimbabwe
Cyclone Idai could prove to be the deadliest storm in generations to hit the impoverished southeast African country of 30 million people.
It struck Beira, an Indian Ocean port city of a half-million people, late on Thursday and then moved inland to Zimbabwe and Malawi with strong winds and heavy rain.
But it took days for the scope of the disaster to come into focus in Mozambique, which has a poor communication and transportation network and a corrupt and inefficient bureaucracy.
Speaking on state Radio Mozambique, Nyusi said that while the official death toll stood at 84, "It appears that we can register more than 1 000 deaths."
More than 215 people were killed by the storm in the three countries, including more than 80 in Zimbabwe's eastern Chimanimani region and more than 50 in Malawi, according to official figures. Hundreds more were reported injured and missing, and nearly 1 000 homes were destroyed in eastern Zimbabwe alone.
Doctors Without Borders said rivers have broken their banks leaving many houses fully submerged and around 11 000 households displaced in Nsanje, in southern Malawi.
UN agencies and the Red Cross helped rush emergency food and medicine by helicopter to the stricken countries.
Mount Chiluvo in central Mozambique was badly hit by flooding. One resident said he heard a loud noise, like an explosion, and suddenly saw a river of mud rolling toward his home.
"I was indoors with my children, but when we looked, we saw mud coming down the road toward the houses and we fled," Francisco Carlitos told Lusa, the Portuguese News Agency. The family lost their home and possessions but safely reached higher ground.
The country's president, who cut short a visit to neighbouring Swaziland over the weekend because of the disaster, spoke after flying by helicopter over Beira and two rural provinces, where he reported widespread devastation.