"Bonds can be seen as a bit of a safe-haven, in the rand market specifically. And with the currency and equities being knocked there's probably been some temporary allocation into bonds," said bonds trader at RMB Michelle Wohlberg.
Local bonds trade at a favourable differential, or carry trade, to those of developed countries offering zero or negative yields, largely due to low inflation and high lending rates.
But the currency, down around 9% since January, has not been able to escape the cocktail of weak economic growth and heightened risk aversion stoked by the increasing number of coronavirus cases outside China.
At 1530 GMT the was 1.02% weaker at 15.1650 per dollar.
The selloff in equities, with the Top-40 index down 4.5% to 49,267 points and the All-Share sliding 4.3% to 54,880 points, was led by miners, consumer goods firms and telecoms.
Miners Amplats, AngloGold Ashanti and Impala Platinum all fell more than 8% as the virus-related risk-off mood paired with a pullback in global platinum and palladium prices.
Retailers also suffered, with clothes seller Foschini shedding 7.5%, while consumer goods firms Tiger Brands and Woolworths tumbled more than 4%, worsened by the negative growth outlook.
Italy, South Korea and Iran reported sharp increases in coronavirus cases over the weekend, giving global markets a scare.
Bianca Botes, an analyst at Peregrine Treasury, said the toll on global growth of the virus outbreak was likely to be larger than initial forecasts, pushing investors out of emerging markets even as they were still on the hunt for yields.
"The carry trade will always be important. People will always be seeking yield. The question is how much of that is coming into South Africa. If it wasn't for the carry trade supporting the rand, it could have been trading around 15.50 by now," Botes said.
A Reuters poll this month forecast 2020 GDP growth of 0.8%, while a survey last week suggested the Treasury will raise taxes in the Feb. 26 budget to increase revenues and ward off a ratings downgrade to junk status by Moody's.
"Depending what the finance minister says on Wednesday, anything like increases in company taxes or VAT, would hit the retailers hard," said analyst at Unum Capital Lester Davids, warning that bargain-hunting at the moment was too risky.