Rallying for the third straight session, the Sensex at the Bombay Stock Exchange gained 131 points, or 0.7 percent, to 19,602, amid firm global markets on Thursday. The Nifty at the National Stock Exchange rose 33 points, or 0.6 percent, to 5,885.Stock markets in Japan, China, Hong Kong, South Korea and Singapore gained between 0.7 percent and 1.4 percent.