SEOUL — South Korea's benchmark KOSPI index tumbled nearly 4% on Wednesday, one of its steepest single-day drops in weeks, as renewed U.S. strikes on Iran sent oil prices higher and fueled a punishing selloff in global bond markets that dragged down semiconductor heavyweights Samsung Electronics and SK Hynix.

The KOSPI stood at 6,569.16 points, down 266.64 points, or 3.90%, in trading around 3:05 p.m. local time, according to Korea Exchange data. The decline erased much of the modest gains the index had posted a day earlier, when it closed at 6,835.80 points after a session driven largely by domestic share buybacks from Samsung and SK Hynix.

Wednesday's rout came after the United States launched fresh military strikes against Iran, escalating a conflict now in its seventh month and reigniting fears over disruptions to global energy supplies. The attacks pushed crude oil prices sharply higher overnight, stoking concerns that renewed inflation pressure could force central banks worldwide, including South Korea's, to keep interest rates elevated for longer.

The sell-off was broad-based, but semiconductor stocks — which together account for more than half of the KOSPI's total market weight — led the market lower. Samsung Electronics and SK Hynix, the two chipmakers that have powered much of the index's rally this year on the back of surging artificial intelligence demand, both fell sharply, with declines that widened as the session progressed. Other major exporters........

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