An electronic board showing the Korea Composite Stock Price Index at a dealing room of the Hana Bank headquarters in Seoul on Tuesday. (Yonhap) Seoul shares plummeted nearly 5 percent Tuesday as technology stocks extended losses after Samsung Electronics Co. released its preliminary second-quarter earnings estimate. The Korean won fell against the US dollar.After opening 1.6 percent lower, the benchmark Korea Composite Stock Price Index extended losses, falling 395.02 points, or 4.91 percent, to close at 7,656.31.Trade volume was heavy at 512.29 million shares worth 39.66 trillion won ($25.9 billion), with decliners outnumbering gainers 509 to 358.Institutions and foreigners sold a net 309.1 billion won and 2.92 trillion won worth of stocks, respectively, while individuals purchased a net 3.13 trillion won.Technology stocks plunged on profit-taking after Samsung Electronics estimated its operating profit for the April-June period at 89.4 trillion won, beating market forecasts.Investors are now focusing on whether rising capital spending, intensifying competition and expanding production capacity will generate the earnings growth needed to justify elevated valuations of technology companies, analysts said.In Seoul, technology shares led the decline.Market bellwether Samsung Electronics plunged 6.92 percent to 296,000 won, while chip giant SK hynix declined 6.06 percent to 2,201,000 won ahead of its planned US$29 billion US listing later this week.Top carmaker Hyundai Motor dropped 4.48 percent to 479,000 won, and defense company Hanwha Aerospace shed 3.19 percent to 1,122,000 won.Hanwha Ocean plunged 22.65 percent to 89,800 won after a South Korean consortium that includes the shipbuilder failed to win Canada's multibillion-dollar submarine procurement project.Among gainers, cosmetics maker Amorepacific rose 4.2 percent to 126,500 won, and leading refiner SK Innovation climbed 7.56 percent to 103,800 won.The Korean won was trading at 1,528.20 won per US dollar as of 3:30 p.m., down 2.1 won from the previous session.The Korea Exchange, the country's bourse operator, meanwhile, activated a circuit breaker for the benchmark index, suspending trading of Kospi-listed shares for 20 minutes after the index plunged more than 8 percent during the session. (Yonhap)