Building on initial gains, the Sensex at the Bombay Stock Exchange had rallied a good 260 points, or 1.3 percent, to 20,872 after the Reserve Bank kept key policy rates unchanged in its policy review. Earlier in the morning, the Sensex had climbed 58 points, or 0.3 per cent, to 20,670 on buying by funds and retail investors, ahead of the RBI's policy review.Elsewhere in Asia, stock markets in Japan, Hong Kong, South Korea, China, Taiwan and Singapore were trading mixed, today, as investors awaited the US Federal Reserve's decision on its monetary stimulus program. Over on Wall Street, the Dow Jones Industrial Averge had declined marginally, in yesterday's trade.