10, 000 South African soldiers have been deployed to assist the overwhelmed relief effort in KwaZulu-Natal province where more than 440 people died and dozens more went missing in floods and mudslides caused by a week-long downpour.
The South African National Defence Force (SANDF) would also provide medical support and helicopters for rescue and reconnaissance missions.
President Cyril Ramaphosa in a televised speech on Monday declared a national state of disaster because of the floods and extreme weather in several other provinces.
This would allow for a more effective response to the crisis, he said.
The authorities expect hundreds of millions of euros in damage.
According to Ramaphosa, the finance minister would approach parliament over additional spending, beyond the 1 billion rand ($68 million) which he has said is immediately available.
Children are due to return to school on Tuesday after the long Easter weekend. But authorities have warned that at least 270,000 pupils will be out of school. More than 600 schools have been affected, nearly 4,000 homes destroyed and more than 13,500 damaged.
The latest death toll from the floods stands at 443, with 48 people still unaccounted for, Ramaphosa said.