The Sensex at the Bombay Stock Exchange plunged 367 points, or 2.2 percent, to a nearly four-month closing low of 16,546, on across-the-board selling by investors, amid falling European markets, today. The Nifty at the National Stock Exchange lost 114 points, or 2.2 percent, to 5,000.Stock markets in Japan, China, Hong Kong, Singapore and South Korea ended mixed.