The rand rallied to its firmest since April 26, scaling 13.1575 per dollar in afternoon trading, before paring gains to 1.35 percent at 13.1700 by 1629 GMT.

The greenback retreated as the New York Federal Reserve's barometer on business activity in the state unexpectedly fell in May, sinking into negative territory for the first time since October, and following weak data on Friday.

A missile test by North Korea over the weekend also weighed on sentiment, allowing emerging market currencies to gain against the greenback.

South African government bonds firmed alongside the currency with the yield for the benchmark paper due in 2026 down 2 basis points to 8.685 percent.

On the bourse, stocks were mixed, with the benchmark Top-40 index advancing 0.01 percent to 47,436 points and the broader All-share index declining 0.02 percent to 54,052 points.

Platinum miner Lonmin lost the most ground, falling 11.6 percent to 17.91 rand, after reporting a drop in half-year production and higher costs.

Lonmin, which has all its mines in South Africa, reported a loss per share of 64.4 cents versus 1.8 cents, while unit costs were higher driven by the weak mining performance.

"Longer term, we continue to argue that the company faces significant structural head winds," Citi analyst Johann Steyn said in note, adding that Lonmin was its least preferred South Africa platinum stock.

Aspen Pharmacare slid 3.6 percent to 275.31 rand after EU antitrust regulators said it will investigate whether the drugmaker is charging excessive prices for five key cancer drugs.

The bourse's biggest gainer was Barloworld, which is southern Africa's largest dealer of Caterpillar CAT.N mining trucks. Barloworld shares gained 5.1 percent to 119.99 rand after the firm reported a 9 percent half-year profit rise.