Foreign institutional investors (FIIs) bought shares worth a net Rs 511.15 crore on Wednesday, as per provisional data from the stock exchanges.
The 30-share index Sensex resumed higher at 20,995.39 points and firmed up further to 21,120.25 on initial strong buying.
However, it declined afterwards to 20,989.66 points before quoting at 21,057.23 at 1100 hours, still showing a gain of 70.24 points, or 0.33 per cent, from its last close.
Major gainers were Hindalco 3.51 pct, Tata Motors 3.33 pct, Dr Reddy's Lab 2.78 pct, TCS 2.69 pct, Sun Pharma 1.82 pct, Axis Bank 1.76 pct, BHEL 1.57 pct and ONGC 1.06 pct.
Asian stocks edged lower in their early trade weighed by tensions in Ukraine.
Key benchmark indices in Hong Kong, Singapore, China, Japan and South Korea fell by 0.19 to 0.95 per cent.