The 30-share BSE index, which gained 132.16 points in the previous session, declined by 65.19 points, or 0.41 per cent, to 15,937.32 in opening trade.
In a similar fashion, the wide-based National Stock Exchange Nifty index shed 22.45 points, or 0.46 per cent, to 4,778.15. Oil and gas, power, PSU, metal and capital goods stocks led the fall.
Brokers said fresh selling by funds in tandem with a weak trend on other Asian bourses following an overnight fall on Wall Street amid the persisting euro zone debt crisis was mainly responsible for the early decline on the bourses.
Meanwhile, in the Asia region, Hong Kong's Hang Seng Index fell by 0.68 per cent and Japan's Nikkei Index by 0.46 per cent in early trade today.
The Dow Jones Industrial Average in the US ended 0.55 per cent lower yesterday.