The Bombay Stock Exchange benchmark Sensex on Tuesday fell by over 71 points, or 0.44 per cent in opening trade on fresh selling by funds, triggered by a weak trend in the global markets.The 30-share Sensex, which had gained 19.96 points in on Monday's choppy trade, fell by 71.54 points to 15,864.07 points in early trade as stocks of banking, oil and gas and realty sectors declined.The wide-based National Stock Exchange index Nifty also drifted by 20.25 points to 4,740.15.In the global markets, Japanese share opened lower on Tuesday, in line with the trend in the West. Nikkei-225 index fell 72.92 points to 9,878.90 in the first minutes of trade.The US stocks had on Monday dropped sharply amid worries about debt problems in the eurozone, sending the Dow Jones industrials to a close below 10,000 for the first time since November.