Extending its gains for the sixth straight session, the Sensex at the Bombay Stock Exchange closed 50 points, or 0.3 percent higher, at 17,463, on Wednesday. The Sensex rose on reports of higher quarterly tax payments by domestic companies, and firm Asian bourses. The Nifty at the National Stock Exchange rose 11 points, or 0.2 percent, to 5,233.Stock markets in Japan, Singapore and South Korea gained between 1 percent and 1.8 percent.