Hundreds are missing in Mozambique and its president said he fears the death toll may ultimately top 1,000.
Bad weather and building damage have impeded military and humanitarian efforts, but officials said rescue efforts kicked into high gear Tuesday to find the missing.
In Zimbabwe, a landslide blocked access to the town of Chimanimani, but aid agencies did reach some lower altitude regions. Officials said Idai killed at least 98 people there and more than 200 are missing. Dozens have also died in Malawi.
Cyclones are not uncommon in southern Africa, but forecasters say Indai is the most powerful since Cyclone Eline in 2000.
South African foreign minister Lindiwe Sisulu appealed Monday for donations to buy supplies for displaced persons in Malawi, Zimbabwe and Mozambique.
UNICEF USA is also calling for support with a fundraiser called “You Can Make a Difference Right Now.”