Seoul shares plunged more than 12 percent Wednesday, closing below the 5,100-point mark, as mounting concerns over the economic fallout from the escalating Middle East conflict rattled investor sentiment. The Korean won also fell sharply against the U.S. dollar. The benchmark Korea Composite Stock Price Index (KOSPI) tumbled 698.37 points, or 12.06 percent, to close at 5,093.54, extending losses from a 7.24 percent drop in the previous session. The 12.06 percent fall marked the steepest one-day