The Sensex at the Bombay Stock Exchange declined 151 points, or 0.7 percent, to close at 20,709, today. The Sensex fell after the US Federal Reserve, or central bank, said it would cut its monthly bond purchases by 10 billion dollars, to 75 billion dollars from next month. The Nifty at the National Stock Exchange fell 51 points, or 0.8 percent, to 6,167.Stock markets in Japan, China, Hong Kong, South Korea and Singapore ended mixed.