Cyclone Idai has had a “massive and horrifying” impact on Mozambique’s port city of Beira, the Red Cross says.
It made landfall on Thursday with winds of up to 177 km/h (106 mph), but aid teams only reached Beira on Sunday.
People have been rescued from trees, homes have been destroyed and roofs were ripped off concrete buildings, head of the Red Cross assessment team, Jamie LeSeur, told the BBC.
The cyclone has killed at least 150 people across southern Africa.
More than 80 people have died in eastern and southern Zimbabwe, information ministry head Nick Mangwana told Reuters news agency.
This includes two boarding school pupils in the district of Chimanimani, who died after their dormitory was hit when rocks swept down a mountain.
At least 68 people have died in Mozambique, mostly around Beira, the authorities there say.
Malawi has also been badly hit. The flooding there, caused by the rains before the cyclone made landfall, led to at least 122 deaths, Reliefweb reports.
Local people in Beira, with a population of 500,000, have put in an “incredible effort” to reopen roads in the city, Mr LeSeur told the BBC’s Newsday programme.
“Beira has been severely battered. But we are hearing that the situation outside the city could be even worse,” a statement from the International Federation of Red Cross and Red Crescent Society quotes him as saying.