The Bombay Stock Exchange benchmark Sensex gained 142 points in the initial trade on buying in heavy-weight stocks led by Reliance Power.
The Sensex added 141.57 points to 18,256.82 in the first five minutes of trade. Reliance Industries, Infosys and Tata Steel also registered gains.
The wide-based National Stock Exchange's Nifty rose by 45.70 points to 5,348.60 points.
Buying activity gathered momentum following reports of Anil Ambani's Reliance Power planning to offer bonus shares to compensate for losses to the investors on the first day of its listing.