The Bombay Stock Exchange benchmark Sensex fell by over 261 points in opening trade. The 30-share Sensex, which opened 112 points lower, declined by 261.27 points, or 1.39 per cent, to 18,460.12 in the first few minutes of trade today. In a similar fashion, the wide-based National Stock Exchange Nifty index slid by 80.65 points, or 1.43 per cent,to 5,535.45 points.