The rand hit a week's low of R10.2152 after ending Friday's session at R9.9700, edging closer to last month's four-year low of R10.2850. It was at R10.1750 by 13:48, down 2% from the previous close.
"We've got very weak fundamentals here; our economy is not growing, we've got labour issues. None of that stuff has gone away," said Ion de Vleeschauwer, forex trader at Bidvest Bank.
"It's just really back to the normal problems that the rand has had for the last couple of months."
The yield on the benchmark 2026 issue surged 34 basis points to 8.285%, the highest since mid June 2012.
The shorter-dated 2015 paper also scaled a year-long peak of 6.37%, a 21 basis point jump from Friday.
"It's negative sentiment toward the country, from the foreign perspective a lot of investors have just stopped buying South African bonds," said Victor Mphaphuli, senior portfolio manager for fixed income at Stanlib.
Investors have hammered South African assets - on concerns that labour unrest in the mining industry - which killed more than 50 people late last year - will hobble growth.
The rand is down more than 20% against the greenback since the start of the year, Reuters data showed on Monday, outperforming only the Venezuelan bolivar and the Syrian pound, among global currencies.
Bond yields have also leapt higher after Reserve Bank Governor Gill Marcus dampened hopes of an interest rate cut last week, saying the increasingly risky inflation outlook caused by a weak rand limited the scope to loosen policy.
In addition, markets are bracing for a pull out from higher-yielding but riskier emerging market assets amid expectations US Federal Reserve could wind back its quantitative easing programme.
"The risk still lies in further rand weakness over the coming week in part due to the risk-off and strong dollar trading environment, but also because of lingering South Africa specific risks," said Absa Capital in a market note.
Manufacturing production and retail sales data due out on Tuesday and Wednesday respectively might add pressure on the currency if it surprises on the downside.
Last week the central bank's Marcus said there was a real threat of further credit downgrades after Moody's, Standard and Poor's and Fitch all lowered the country's rating, citing concerns about policy stability in Africa's biggest economy.
"Recent local developments have raised the probability of further downgrades in South Africa's rating to close on 50/50, particularly by S&P and Moody's," said Standard Bank strategist Kuvasha Naidoo.