Extending its losses for the third straight session, the Sensex at the Bombay Stock Exchange slumped 310 points, or 1.7 percent, to a three-week low of 18,412, today. The Sensex fell on heavy selling by investors, after disappointing first quarter results from IT major, Infosys, poor industrial output data, and amid weak global markets. The Sensex had lost 356 points in the previous two sessions. The Nifty at the National Stock Exchange slipped 90 points, or 1.6 percent, to 5,526.Stock markets in Japan, China, Hong Kong, South Korea, and Singapore dropped between 1.5 percent and 3 percent, as worries that Europe's debt crisis would spread spooked investors.