South Korean stocks plunged more than 7 percent Tuesday to close below the 5,800-point mark as investor sentiment was dampened by escalating geopolitical concerns triggered by the ongoing Middle East conflict. The Korean won lost sharply against the U.S. dollar. The benchmark Korea Composite Stock Price Index (KOSPI) tumbled 452.22 points, or 7.24 percent, to close at 5,791.91, marking the lowest closing price since Feb. 20, when the index finished at 5,808.53. It marked the largest-ever daily