(LEAD) Seoul shares plunge over 5 pct on AI regulation concerns after U.S. midterms

Seoul's stock market tumbled over 5 percent Thursday after the Democratic Party's decisive victory in the U.S. midterm elections raised concerns over stricter regulation of artificial intelligence (AI) investments. The Korea Composite Stock Price Index (KOSPI) dropped 300 points, or 5.28 percent, to close at 5,383.80.

The market initially opened 1.82 percent lower, prompting the bourse operator to suspend program trading for five minutes at 10:16 a.m. to stabilize prices. Throughout the day, trade volume remained light at 256.8 million shares, worth 22.6 trillion won (US$16.8 billion). There was a net outflow of 3.39 trillion won from foreigners and a net inflow of 841.8 billion won and 2.28 trillion won from institutions and individuals, respectively.

Kim Seok-hwan, an analyst at Mirae Asset Securities, explained that the Democrats' "blue wave" victory could lead to tighter regulations on AI data centers, potentially impacting investment in the sector. The index's decline hit semiconductor-related shares hard, with Samsung Electronics and SK hynix both falling more than 9 percent.

Other affected firms included Hanmi Semiconductor and Samsung Electro-Mechanics. The broader tech sector also suffered, with Hyundai Motor and Kia increasing slightly, while electric vehicle leader Hyundai Motor rose 3.53 percent. Meanwhile, SK Innovation and Hanwha Aerospace both dipped.

The South Korean won weakened against the U.S. dollar, closing at 1,342.1 won, down 0.6 won from the previous session's close.