 "Market extend losses; heavyweights weigh")
At 1130 hrs, the Sensex was down 33.35 at 20,391 and the Nifty slipped by 13 points to trade at 6,046 levels.
In the broader markets, the midcap stocks continued to trade in green and the BSE mid-cap index was up 0.1% and the smallcap index was down 0.1%.
The rupee was quoting higher on corporate dollar inflows, with the pair at 62.31 versus its previous close of 62.50/51.
Among the sectoral indices, banking index, Bankex down 0.3% was the top loser followed by Teck, Power, IT, Realty and Health Care indices were down 0.1-0.2%.
On the other hand, Auto, Oil & Gas, FMCG, PSU, Consumer Durables and Capital Goods indices gained 0.2-0.6%.
Tata Motors up 1.5% along with Dr Reddys Lab, ONGC and Hindlaco up 1% each were teh top gainers among the Sensex-30.
Gail India, ITC, Tata Steel, L&T, reliance Industries, Jindal Steel and Coal India up 0.1-0.7% were the other prominent gainers.
Bharti Airtel down 2% was the top loser followed by Sesa Sterlite, Sun Pharma, HDFC Bank, BHEL, Tata Power, HDFC, Wipro, Cipla and Hindustan Unilever down 0.5-1.6%.
In individual stocks, Wockhardt plunged nearly 14% to Rs 406 on media reports that the U S Food and Drug Administration (US FDA) issued an import alert for the drug maker's Chikalthana facility at Aurangabad.
Cairn India was trading lower by 2% at Rs 319 on the Bombay Stock Exchange (BSE), after the company announced a buyback at a price not more than Rs 335 per share. The company will spend up to Rs 5,725 crore on the buyback.
The market breadth was marginally positive as 841 stocks advanced while 1079 stocks declined on the BSE.