The rand was at 8.8850 to the dollar at 1512 GMT, 0.4 percent weaker than its close in New York on Friday. Trading was thin due to a public holiday in the United States.

South African police said on Monday at least 13 people were injured in a standoff between rival labour unions at an Amplats' mine where there were violent labour clashes last year.

The rand ended 2012 down 5 percent against the dollar, one of the biggest fallers among emerging market currencies, hit by a wave of violent strikes in the mining sector and concerns about sluggish growth and widening current account and fiscal deficits.

The currency has remained vulnerable this year but showed signs of firming at the end of last week. However, any signs of fresh labour unrest could damage sentiment, said Bidvest Bank trader Ion de Vleeschauwer.

"We are all hoping and praying it's not a flare up of the mine violence we had last year," he said. "If that happens, that will be very negative for our sentiment and confidence will be lost again... It's inevitable that if this kind of behaviour continues we will see more rand weakness."

The yield on the benchmark 2026 government bond rose 2 basis points to 7.315 percent, while that on the 2015 paper was 0.5 basis points lower at 5.35 percent.