Trading halted for 20 minutes as heavy foreign, institutional selling hit benchmark index An electronic board shows the Kospi at a dealing room of the Hana Bank headquarters in Seoul on Friday. (Yonhap) South Korean stocks triggered a marketwide circuit breaker on Friday after the Kospi plunged more than 8 percent in intraday trading, capping a volatile week marked by sharp swings in chip-heavy shares.The Korea Exchange suspended trading on the Kospi market for 20 minutes from 12:10 p.m. after the benchmark index remained more than 8 percent below the previous session's close for one minute, meeting the conditions for a circuit breaker.Trading in all Kospi-listed shares, as well as stock index futures and options, was temporarily halted.At the time of the suspension, the Kospi had fallen 731.97 points, or 8.19 percent, to 8,198.33.Earlier in the session, the Korea Exchange also imposed a sell-side sidecar after Kospi 200 futures dropped more than 5 percent.Individuals were net buyers of 3.77 trillion won ($2.44 billion), while foreign and institutional investors sold a net 3.11 trillion won and 732 billion won, respectively.Shares of Samsung Electronics and SK hynix at one point had tumbled more than 9 percent.Han Ji-young, an analyst at Kiwoom Securities, said the sell-off was driven by concerns over weakening demand for memory chips, as well as profit-taking after the Kospi's sharp rebound over the previous two trading sessions.He said semiconductor stocks had led the recent rally, prompting investors to lock in gains. The retreat in chipmakers also triggered selling by passive funds tracking indexes heavily weighted toward semiconductor shares.Still, Han said concerns over memory demand appeared overstated."Most of today's sharp decline can be explained by the market's heavy concentration in semiconductor stocks and the resulting volatility in fund flows," he said.As of 2:42 p.m., the Kospi was down 6.71 percent at 8,336.67.