This photo, taken Thursday, shows the trading room of Hana Bank in Seoul as South Korean stocks fell by more than six percent on tech stock losses amid Middle East tensions. Photo by Yonhap

Seoul shares again plummeted Thursday, led by steep losses in technology heavyweights, as escalating tensions in the Middle East weighed on investor sentiment. The Korean won rose against the U.S. dollar.

After opening 4.45 percent lower, the benchmark Korea Composite Stock Price Index (KOSPI) extended its losses to close at 6,820.60, down 463.81 points, or 6.37 percent from the previous session, after falling as low as 6,730.87.

The Korea Exchange, the country's bourse operator, activated a sell-side sidecar on the KOSPI for 20 minutes at around 9:10 a.m. after the benchmark index fell more than 5 percent.

The decline came after the index surged 6.24 percent Wednesday as softer-than-expected U.S. inflation data eased concerns about near-term Federal Reserve interest rate hikes.