Erasing early gains, the Sensex at the Bombay Stock Exchange dropped 371 points, or 2.2 percent, to a nearly 15-month low of 16,470 on Thursday. The Sensex fell on across-the-board selling, on interest rate fears, and in line with falling Asian and European markets, as fears of a global economic slowdown gripped investors. The Nifty at the National Stock Exchange declined 112 points, or 2.2 percent, to 4,944.Stock markets in Japan, China, Hong Kong and South Korea lost between 1.3 percent and 1.7 percent.