After a positive opening, the Sensex spurted by 252.87 points, or 1.23 per cent, to 20,865.01 at 1120 hours soon after the Reserve Bank announced its mid-quarter policy.
Surprising the investors, the RBI kept key policy rate and the cash reserve ratio unchanged.
The Sensex had lost over 714 points in the last six trading sessions on expectations that the RBI might hike repo rate.
The banking sector index gained the most, rising 2 per cent to 13,052.77, followed by realty index by 1.83 per cent to 1357.17 points.