The Sensex at the Bombay Stock Exchange fell 97 points, or 0.5 percent, to close at 20,768, on profit booking by investors, amid weak global markets, today. The Nifty at the National Stock Exchange lost 24 points, or 0.4 percent, to 6,178. Stock markets in Japan, China, Hong Kong, South Korea and Singapore declined between 0.2 percent and 2 percent.