The owners of the Seacom cable said the exact cause of the fault was “still being investigated”, but was thought to originate off the Kenyan coast.
The cable, finished in 2009, connects South Africa, Tanzania, Kenya, Uganda and Mozambique to Europe and Asia.
Seacom said it has “initiated emergency repairs”, which may take eight days.
“This unexpected failure affects traffic towards both India and Europe. Traffic within Africa is not affected,” it said in a statement.
The firm said it had been working since the fault was first reported on the 5 July to find alternative methods to route internet traffic, including alternative cables.
“These restoration solutions are now being actively implemented.”
When the cable was completed in July 2009, it promised to bring down the cost of a connection and boost internet access across the region. However, experts say that costs are still out of the reach of many people who live in the region.
The fault has so far mostly affected home users, as many businesses in the region have back-up plans for such faults.
It is the second major outage the cable has experienced since it went live.
Outages of this kind happen periodically. A cable cut in the Mediterranean in 2008 temporarily disrupted up to 70% of internet traffic to Egypt and 60% to India.
The company has said a ship will be dispatched to repair the cable.
“Whilst the repair process itself will only take a few hours, the overall process may last a minimum of six to eight days,” it said.
“The actual duration is unpredictable due to external factors such as transit time of the ship, weather conditions and time to locate the cable. For this reason, the estimated duration of this repair remains uncertain.”
Souce: BBC