South Korea's benchmark Kospi index closed 0.6% lower at 6,954.52 points, ending a three-session winning run, with gains in Samsung Electronics giving back some ground. The index had opened higher and climbed as much as 2.5% during intraday trading before reversing course.

Data released by the Bank of Korea on Tuesday showed the country's second-quarter nominal gross domestic product grew at the fastest pace in 47 years, driven by robust exports and artificial intelligence-related investment. According to preliminary figures, real GDP—the key gauge of economic expansion—rose 0.6% in the April-to-June period compared with the prior three months.

That quarterly figure matched the central bank's earlier estimate released last month, although the Bank of Korea revised up growth in construction investment and intellectual property investment by 0.1 percentage point each while trimming government consumption growth by the same margin. As Asia's fourth-largest economy, South Korea contracted 0.1% in the final quarter of last year but rebounded with 1.8% growth in the first quarter of this year.

On an annual basis, the economy expanded 3.7% in the second quarter, continuing the momentum from the 3.8% year-on-year growth recorded in the first quarter. Exports rose 1.3% quarter-on-quarter, supported by strong global demand for semiconductors, machinery, and equipment, though that pace slowed from the 5.9% increase seen in the January-to-March period.

In nominal terms, South Korea's second-quarter GDP grew 9.2% from the previous quarter and 26.4% year-on-year, marking the largest increase since the third quarter of 1979, when the economy expanded 27.7% annually. The central bank data also revealed that gross national income per capita rose 8.8% quarter-on-quarter in nominal terms and 26.4% from a year earlier.

Real GNI climbed 3.1% quarter-on-quarter and 15.6% year-on-year, the steepest gain since the fourth quarter of 1988, when real GNI had grown 15.7% annually.