Seoul's main stock index closed nearly 1% higher on Wednesday, lifted by share buybacks from local chip giants and easing external conditions, while investors awaited earnings from Nvidia. The Korean won weakened against the U.S. dollar during the session.

The benchmark KOSPI advanced 65.47 points, or 0.97%, to settle at 6,808.21. Trading volume was moderate, with 323.3 million shares changing hands, totaling 22.38 trillion won (approximately $16.15 billion). Advancing stocks outnumbered decliners 584 to 273.

The index fluctuated in early trading before gaining momentum as institutional investors turned net buyers, purchasing 760.37 billion won worth of shares. Foreign investors and retail traders were net sellers, offloading a combined 2.36 trillion won.

"The KOSPI reclaimed the 6,800 level, supported by share buybacks, while falling international oil prices and lower U.S. Treasury yields boosted market sentiment," said Lee Kyung-min, an analyst at Daishin Securities.

Chip heavyweight SK Hynix has been conducting a buyback of approximately 650,000 shares since last Thursday, with Samsung Electronics also carrying out its own repurchase program this week. Investors are closely monitoring the upcoming Nvidia earnings report, which is expected to serve as a key barometer for the global artificial intelligence infrastructure market.

Among blue-chip stocks, Samsung Electronics rose 1.75% to 261,500 won, while rival SK Hynix edged up 0.6% to 1,688,000 won. Hyundai Motor fell 3.09% to 408,000 won, and defense contractor Hanwha Aerospace slipped 1.36% to 1,087,000 won. Major financial institution KB Financial Group inched up 0.12% to 166,600 won.

Nuclear power-related stocks strengthened on reports that the U.S. government has proposed that South Korea jointly acquire a stake in Westinghouse Electric, which is currently owned by a Canadian private equity firm. The won was quoted at 1,384.8 per dollar as of 4:30 p.m., up 1.3 won from the previous session.