After rising to 25,197.50 in morning trade in line with positive Asian cues, the Sensex fell back to trade lower by 209.92 points, or 0.83 per cent, to quote at 24,895.59 during midsession.
Stocks of FMCG, IT, tech, consumer durables, oil and gas, power and capital goods led the fall on profit-booking.
The 30-share Sensex had lost over 415 points in the previous three sessions.
Similarly, the National Stock Exchange index Nifty dipped below the crucial 7,500 points by falling 52.60 points, or 0.70 per cent, to 7,458.85 after surging to 7,534.80 at the outset.
Brokers said apart from profit-booking by participants, persistent rise in global crude oil prices on continued unrest in Iraq dampened the trading sentiments.
Besides, a weak trend in global markets too triggered off selling by funds, they said.
Meanwhile, Foreign portfolio investors (FPIs) sold shares worth a net Rs 220.65 crore as on last Friday, as per provisional data from the stock exchanges.
Prominent losers, which dragged down the Sensex, were ITC Ltd at 5.18 per cent, Hindustan Unilever 1.31 per cent, Cipla 1.18 per cent, Infosys 2.38 per cent, Reliance Industries (RIL) 0.95 per cent and GAIL by 1.12 per cent.