At least one person has been killed and dozens are feared trapped under rubble after a section of a shopping centre under construction collapsed in South Africa.

29 people, two in critical condition, were hospitalised after the incident in Tongaat, 30km north of Durban.

It was not immediately clear what caused the three-storey building to collapse.

However, Deputy Mayor Nomvuzo Shabalala said local authorities had tried to halt construction at the site a month ago.

"There are areas of the law that they did not follow in terms of building of this infrastructure," Ms Shabalala told broadcaster ENCA.

"We were not aware that they were continuing building."

As darkness fell over the site, scores of rescue workers and police combed the broken concrete slabs and twisted bits of metal.

Sniffer dogs roamed through the debris looking for survivors as large crowds of relatives gathered behind a security cordon.

"In all my years as a paramedic I have never seen anything like this," said one rescue worker.

Hydraulic jacks were used to lift the slabs or break through the concrete to reach survivors.

Ambulances ferried the injured to nearby hospitals, which initiated full-scale disaster plans.