The Indian equity benchmarks extended gains for second straight session on Thursday led by gains in Reliance Industries, which surged to record high of Rs 2,788.80 on the BSE. The Sensex rallied as much as 954 points and Nifty 50 index briefly surpassed its important psychological level of 17,400. The bnechmarks staged a gap up opening and added to gains on the back of shortcovering rally after the markets went into oversold zone.