Falling for the third straight session, the Sensex at the Bombay Stock Exchange plunged 320 points, or 1.9 percent, to close below the 17,000 level, at 16,831–its lowest level since January 30. The Sensex fell on heavy selling by foreign funds, amid a weak rupee, and subdued regional bourses. The Nifty at the National Stock Exchange lost 102 points, or 2 percent, to 5,087.Stock markets in Hong Kong, Singapore and South Korea shed between 0.3 percent and 0.8 percent.