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South Korean stocks plunged more than 5 percent on June 5, 2026, as investors locked in profits from a recent tech-led rally while monitoring uncertainty over U.S.-Iran peace negotiations, according to Yonhap News Agency. The Korean won weakened sharply against the U.S. dollar.

The benchmark Korea Composite Stock Price Index (KOSPI) lost 478.82 points, or 5.54 percent, to close at 8,160.59, retreating for a second consecutive session. The decline triggered a sidecar, suspending program trading for five minutes after the KOSPI 200 Futures index fell 5 percent or more for at least one minute.

Coverage Comparison

Yonhap News Agency reported the sharp decline across multiple articles, with the KOSPI closing down 5.54 percent on June 5. Other reports from the same day showed the index trading nearly 4 percent lower at 11:20 a.m., recovering some of its earlier losses after plunging as much as 6.88 percent. A separate report noted the index fell 3.88 percent to 8,304.44 at that time.

The decline was attributed to investors locking in profits from a recent tech-led rally, as well as uncertainty over U.S.-Iran peace negotiations. The reports also cited a tech slump on Wall Street, driven by concerns over the valuation of artificial intelligence (AI) stocks.

On June 10, the KOSPI shed 366.11 points, or 4.52 percent, to close at 7,730.82, almost eclipsing the over 8 percent surge from the previous day. This decline was attributed to escalating tensions between the United States and Iran, and a tech slump fueled by concerns over AI stock valuations.

On June 11, the KOSPI started sharply lower, plunging 288.94 points, or 3.74 percent, to 7,441.88 in the first 15 minutes of trading, tracking an overnight tech slump on Wall Street and escalating U.S.-Iran tensions.

On June 17, the KOSPI inched up 11.31 points, or 0.13 percent, to 8,737.91, as of 11:20 a.m., with major tech companies trading lower following a tech slide in the U.S. market overnight.

Key Claims

  • The KOSPI lost 478.82 points, or 5.54 percent, to close at 8,160.59 on June 5, 2026, as reported by Yonhap News Agency.
  • The KOSPI shed 366.11 points, or 4.52 percent, to close at 7,730.82 on June 10, 2026, according to Yonhap News Agency.
  • The KOSPI lost 288.94 points, or 3.74 percent, to 7,441.88 on June 11, 2026, as reported by Yonhap News Agency.
  • The Korean won was quoted at 1,539.1 won against the U.S. dollar at 3:30 p.m. on June 5, down 9.4 won from the previous session.
  • Foreign investors extended their selling streak to a 20th consecutive session on June 5, and to a 23rd consecutive session on June 10, with a net sell-off of 3.5 trillion won on June 5 and 2.77 trillion won on June 10.
  • Oil prices retreated after three consecutive sessions of gains on June 5, as investor sentiment improved following reports that Israel had agreed to a conditional ceasefire with Lebanon.
  • On June 11, the U.S. launched additional strikes against Iran, and Iran threatened to fire on any vessel attempting to pass through the Strait of Hormuz, as reported by Yonhap News Agency.
  • The U.S. Consumer Price Index for May, released on June 11, was softer than expected but not enough to soothe concerns over a possible hawkish policy pivot by the U.S. Federal Reserve, according to Seo Sang-young, an analyst at Mirae Asset Securities.
The Korean won weakened against the U.S. dollar across the period. On June 5, it was quoted at 1,539.1 won at 3:30 p.m., down 9.4 won, and at 1,546.1 won at 11:20 a.m., down 16.4 won. On June 17, it was trading at 1,513.4 won, down 1.8 won from the previous session.

Market heavyweights led the declines. On June 5, Samsung Electronics fell 3.56 percent, SK hynix sank 5.96 percent, and LG Electronics shed 8.23 percent. On June 11, Samsung Electronics shed 3.47 percent, SK hynix fell 2.54 percent, and SK Square plummeted 7.86 percent.

The sharp falls triggered trading halts. On June 5, the Korea Exchange suspended program trading for the KOSPI for five minutes at 9:08 a.m. as a sidecar was triggered. On June 10, a sell-side sidecar was activated at 1:16 a.m., halting program trading for five minutes.