Rising for the third straight session, the Sensex at the Bombay Stock Exchange gained 34 points, or 0.2 percent, to 17,392, on sustained buying by investors, amid positive Asian markets, today. The Sensex had gained more than 260 points in the previous two trading sessions. The Nifty at the National Stock Exchange rose 10 points, or 0.2 percent, to 5,300. Stock markets in Japan, China, Hong Kong, South Korea and Singapore advanced between 0.5 percent and 2 percent.