▲ Financial data is shown on a screen inside the dealing room of Hana Bank in central Seoul on Sept. 7, 2026. (Yonhap)

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SEOUL, Sept. 7 (Yonhap) -- South Korean shares surged 4.6 percent to a more than five-week high Monday as OpenAI's new-generation model fueled demand for artificial intelligence (AI)-related shares. The Korean won rose against the U.S. dollar.

The benchmark Korea Composite Stock Price Index (KOSPI) closed up 308.18, or 4.61 percent, to 6,995.39, extending its winning streak to three sessions.

It marked the highest closing since July 23, when the KOSPI finished at 7,096.89.

Trade volume was light at 237.9 million shares worth 21.5 trillion won (US$16 billion), with gainers beating decliners 476 to 380.

The index was lifted by foreign and institutional investors, who scooped up a net 2.55 trillion won and 2.64 trillion won, respectively. However, individual investors dumped a net 6.83 trillion won.

The index started 3.34 percent higher as investors were boosted by the launch of OpenAI's new GPT-6 Astra, which is expected to boost demand for memory chips.

While three major U.S. stock indexes closed lower on Friday, the PHLX semiconductor index rose 3.38 percent.

"Despite sluggish major tech and software shares on Wall Street, investor sentiment was stoked by OpenAI's new Astra, which could open up the artificial general intelligence (AGI) era," said Kang Jin-hyuk, a senior analyst at Shinhan Securities.

Semiconductor shares were among the biggest winners as industry leader Samsung Electronics jumped 5.68 percent to 270,000 won, and its rival SK hynix soared 8.26 percent to 1.78 million won.

Hanmi Semiconductor, a leading chip equipment maker, rose 4.57 percent to 240,500 won, and SK Square, parent of SK hynix, vaulted 8.07 percent to 1.13 million won.

Top carmaker Hyundai Motor added 2.48 percent to 393,000 won, and its auto parts affiliate Hyundai Mobis climbed 2.37 percent to 432,000 won.

Bank shares were also bullish as Hana Financial Group advanced 3.43 percent to 138,900 won, and Shinhan Financial Group mounted 3.26 percent to 113,900 won.

Defense firms closed mixed as LIG D&A gained 1.07 percent to 659,000, won but Hanwha Aerospace fell 1.52 percent to 1.04 million won.

The Korean won was quoted at 1,340.5 won against the U.S. dollar as of 3:30 p.m., up 9.9 won from the previous stock trading session.

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