Extending its gains for the fourth straight session, the Sensex at the Bombay Stock Exchange rose 59 points, to close at 17,578, today, on continued buying interest, after global rating agency, Standard and Poor's upgraded the country's outlook from negative to stable. The Nifty at the National Stock Exchange added 17 points, or 0.3 percent, to 5,263.Stock markets in Japan, China, Hong Kong, and South Korea rose between 0.2 percent and 0.8 percent.