WATCH | KZN floods: Search for bodies continues as death toll approaches 70
"Around 70" people are believed to have been killed after heavy rains caused flooding and mudslides along the KZN coast, acting premier Sihle Zikalala said on Thursday.
Final figures are expected to be released during the day.
Flooding also killed at least three people in neighbouring Eastern Cape.
The rains mainly hit areas around Durban. Multiple dwellings collapsed in mudslides, said Robert McKenzie, a KZN Emergency Medical Services spokesperson.
Rescue workers were digging through collapsed buildings on Wednesday.
Victor da Silva, a resident of the coastal town of Amanzimtoti, said his family managed to evacuate before the floods destroyed their home and cars.
"On Monday, the water was just crazy. And yesterday morning I got here everything was fine, my garage was still here, the other part of the house was still here, and it just couldn't stop raining," Da Silva said. "And then an hour and a half later everything poof (vanished) because the rain just hasn't stopped."
Johan Fourie said he fled his home in Amanzimtoti just before part of it collapsed.
"I nearly lost my life, and my neighbour, I believe, is in hospital," Fourie told eNCA.
The region had been hit by heavy rains for days, but authorities did not foresee the extent of the downpour late on Monday, said Lennox Mabaso, a spokesperson for the provincial co-operative governance and traditional affairs department.
"As a result, there was flooding and some structures were undermined and collapsed on people," Mabaso said.
Some people were swept away by the water, he added.
President Cyril Ramaphosa visited affected communities on Wednesday and is expected in the Eastern Cape in the next few days.
"This is partly what climate change is about, that it just hits when we least expect it," he said.
The president commended the public for pulling together in trying times.
"There have been outstanding rescues and lifesaving feats by many people, who jumped into the mud, who jumped into flowing water to save their children, their loved ones and other friends and neighbours," he said.
"We commend our people for taking risky actions the way that they did."
Last week 13 people were killed during an Easter service in KZN when a church wall collapsed after days of heavy rains and strong winds.