The death toll from floods on South Africa's eastern coast continued to rise over the weekend as rescuers searched for those still missing, said authorities who predict the disaster to be among the country's worst.

Sihle Zikalala, the premier of KwaZulu-Natal, told reporters during a press briefing n Sunday, six days after heavy rain battered the eastern coastal province, causing mass flooding, that 443 people were now confirmed dead.

He said it was one of the worst catastrophes to befall KwaZulu-Natal and expects the human and financial toll to surpass that of floods that hit the province in 1987, resulting in the deaths of more than 500 people and an estimated $500 million in damages.

"The loss of life, destruction of homes, the damage to the physical infrastructure, the demolition of public buildings, and the consequent damage to services combine to make this natural disaster one of the worst ever in recorded history of our province," he said.

Over the weekend, authorities focused on rescuing people from the wreckage caused by flooding, but such efforts had only just begun with 63 residents still unaccounted for, he said.

On Sunday, President Cyril Ramaphosa announced the postponement of a scheduled visit to Saudi Arabia for Tuesday in order to focus on the government's response to the flood.

"We are standing by the people of KwaZulu-Natal through the provision of social and material support to thousands of households and a vast number of businesses that have been affected by this catastrophe," he said in a statement. "We have also been touched by the expressions of concern and solidarity, and offers of assistance expressed by many countries around the world."