Transnet, which operates major South African ports, including Durban and Cape Town, and a huge railway network that transports minerals and other commodities for export, confirmed it was experiencing disruptions to its IT applications and was identifying the source.

Two of the sources said the attack occurred early on Thursday.

Transnet said its container terminals were impacted by the disruption while its freight rail, pipelines, engineering and property divisions were reporting normal activity.

"We were told it's a cyber attack," said a source at Durban port, one of the busiest ports in Africa.

Durban is a hub for exports including agricultural commodities, minerals and imports such as crude oil and petroleum products.

Transnet's official website was also down on Thursday showing an error message.

(Reporting by Zandi Shabalala and Tanisha Heiberg; editing by Jason Neely and Susan Fenton)

By Zandi Shabalala and Tanisha Heiberg