The Sensex opened at 20,913.79, compared with Friday's close of 20,851.33, on initial buying and then declined to 20,740.63 on selling pressure.
It recovered afterwards to 20,822.11 at 1030 hrs, still showing a loss of 29.22 points, or 0.14 per cent, from the previous closing level.
The 50-share CNX Nifty on the National Stock Exchange moved down 9.35 points, or 0.15 per cent, to 6,201.80 at 1030 hrs.
ONGC firmed up 3.17 per cent, Tata Motors 1.42 per cent and Larsen & Toubro 1.07 per cent.
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Foreign institutional investors sold shares worth a net Rs 18.06 crore on Friday, according to provisional data from the stock exchanges.
Most Asian stocks were lower as an index of China's services industry declined last month.
Key indices in Taiwan, Hong Kong, China and Japan fell, while those in Singapore and South Korea rose.