Falling for the sixth straight session, the Sensex at the Bombay Stock Exchange plunged 314 points, or 1.9 percent, to close at a 6-week low of 16,462, on across-the-board-selling by investors, amid weak European markets, today. The Nifty at the National Stock Exchange fell 96 points, or 1.9 percent, to 4,935.Stock markets in Japan, China, Hong Kong, South Korea and Singapore ended mixed.