The Bombay Stock Exchange benchmark Sensex extended its gain to over 150 points in afternoon trade today, close to 16,600 points. The 30-share index, which had ended with losses yesterday, started the session in green and rose 36 points to 16,477 in opening trade. The wide-based National Stock Exchange index Nifty also saw an upward trend by 45 points and is trading above 4,900 mark .