South Korean shares closed sharply lower on Thursday, October 15, after an intraday plunge triggered a 20-minute halt in trading on the country’s main stock market. The benchmark KOSPI finished at 5,554.22, down 454.59 points, or 7.57%, according to closing figures reported independently by Reuters and Yonhap News Agency. The index had dropped more than 8% during the session, crossing the Korea Exchange’s first circuit-breaker threshold, before trimming some of its losses.

A pause, not a market shutdown

The Korea Exchange stopped trading on the KOSPI market at 12:38 p.m. Korea Standard Time, Yonhap reported. Trading resumed after 20 minutes. South Korea’s government explanation of the exchange rules says the first-stage circuit breaker applies when the KOSPI falls at least 8% from the previous close for one minute. The mechanism gives participants a pause during a rapid decline; it does not establish a price floor or guarantee a rebound.

Related reporting: Sui Foundation Invests $30 Million as DATA Network Plans Migration

Earlier in the session, the exchange also briefly suspended program selling through a separate sell-side ‘sidecar’ measure tied to KOSPI 200 futures, according to Yonhap. The distinction matters: the sidecar affects program orders for five minutes, while the later circuit breaker halted trading across the main board. The KOSPI’s final 7.57% decline was smaller than its steepest intraday fall, but the close was still its lowest since April 7. It was the index’s seventh consecutive losing session.

Chipmakers drove the decline

The largest semiconductor shares accounted for much of the pressure. Samsung Electronics fell 9.48% and SK Hynix lost 11.06% at the close, Yonhap reported. Both are major components of the South Korean market and suppliers to the global technology industry, so sharp moves in their shares can have an outsized effect on the headline index. Declining stocks substantially outnumbered gainers: Yonhap counted 787 decliners against 112 advancers.

Foreign investors were net sellers of about 3.62 trillion won in South Korean shares, while domestic institutions and individuals were net buyers, Yonhap reported. Those flows describe Thursday’s trading, not a settled judgment on the companies’ longer-term earnings. Reuters also reported that South Korean government and financial officials held an emergency meeting and pledged measures aimed at market stability and investor protection. The public statements do not by themselves indicate that a particular intervention will reverse the selloff.

Global pressures, with no single proven cause

The decline came amid a broader reassessment of technology shares. Reuters linked the Korean selloff to weakness in semiconductor stocks and worries about the scale of artificial-intelligence investment. Yonhap also pointed to hotter-than-expected U.S. inflation data and the possibility that borrowing costs could remain elevated or rise further. Those factors can weigh on richly valued growth shares, but the reports do not establish how much of Thursday’s move each factor caused.

For investors beyond Korea, the session highlights how a change in expectations for U.S. interest rates or AI spending can travel through globally connected equity markets. Korean memory-chip producers sit in supply chains used by data centers and consumer devices, while international funds trade their shares alongside other technology holdings. The halt was a domestic market safeguard, yet the underlying concerns were not confined to Seoul.

What to watch next

The immediate questions are whether selling in chipmakers eases, whether foreign outflows continue and how policymakers respond if volatility persists. A one-day circuit breaker is a measure of the speed of the decline, not a forecast of the next session. Company results, U.S. inflation and rate expectations, and evidence about actual AI-related demand will matter more for the eventual direction of these shares than the halt alone.

Sources

AI-generated editorial image; not a photograph of the reported event. Prepared with AI assistance and source verification.