The Sensex, which had lost 219 points in the last three trading sessions, fell further by 140.90 points, or 0.80 per cent to 17,490.81 led by stocks of realty, metal and auto sectors.
NSE 50-scrip index Nifty dipped below the psychological 5,300 level after August 10 to end with a loss of 46.80 points, or 0.88 per cent to 5,287.80.
Brokers said selling pressure gathered momentum as major market players squared positions ahead of the settlement in this month's derivatives contracts and the first quarter GDP data on Friday.
They said the stock market also turned cautious amid concerns that policymakers have limited room to boost the weakening economy, amid political logjam on the CAG report on coal block allocations.
Sentiment further dampened on a weakening trend in global markets on deepening euro-zone debt crisis and lower earnings by leading companies.
As many as 21 stocks in the Sensex declined, while HDFC Bank ended unchanged.