The Sensex at the Bombay Stock Exchange gained 31 points, or 0.2 percent, to close at a 33-month high of 20,476, on sustained buying by foreign funds, today. The Nifty at the National Stock Exchange rose 16 points, or 0.3 percent, to 6,159. Stock markets in HongKong, Singapore and South Korea rose between 0.1 percent and 1 percent.