By 1250 GMT, the benchmark FTSE/JSE all share index had fallen 2% to 53,068 points, losing ground regained on Wednesday and sending it back to levels seen a day earlier, when the stock markets topped off a six-day losing streak.
The bluechip FTSE/JSE top 40 companies index was trading down 2.21% at 49,017 points.
The broad-based rout, which saw shares from real estate to technology tank, was led by index heavyweight Naspers Ltd, down about 4% in afternoon trade.
Naspers, along with subsidiary Prosus, hold a weight of almost a quarter in major South African indices.
South Africa's rand also slipped way past the sentimental 17 rand per dollar mark on Friday, paring gains seen in early trade as the second wave of coronavirus in Europe dampened hopes of faster economic recovery and moved investors away from riskier currencies.
At 1250 GMT the rand was 1.12% down at 17.1450 per dollar, following a close of 16.9400 overnight in New York in low volume trade with local markets closed for a national holiday.
After rallying to a six-month high of 16.0950 last Friday, the rand and other risk assets have reversed course. It has weakened more than 6% as fears of a second wave of COVID-19 infections in Europe rattled investor sentiment.
"Another driver of this week's risk-off frenzy has been the realisation that the Fed stimulus the market has become so accustomed to in recent months will eventually reach an end," said economists at ETM Analytics.
Bonds inched lower, with the yield on the benchmark 2030 government issue up 1 basis point to 9.50%.
(Reporting by Mfuneko Toyana and Promit Mukherjee; Editing by Alex Richardson and Vinay Dwivedi)
