Extending its losses for the fifth straight session, the Sensex at the Bombay Stock Exchange plunged 211 points, or 1.2 percent, to close at a seven-month low of 18,226, on all-round selling pressure, today. The Sensex has now declined more than 810 points in the last five trading sessions. The Nifty at the National Stock Exchange lost 48 points, or 0.9 percent, to 5,495.But stock markets in China, Hong Kong, South Korea and Singapore gained between 0.1 percent and 0.7 percent.