The Bombay Stock Exchange benchmark Sensex fell by over 56 points in opening trade on Thursday as funds and retail investors booked profits amid weak global markets. The 30-share index dipped by 56.74 points, or 0.34 per cent, to 16,331.10 in opening trade after surging 365.36 points in Wednesday's trading. The National Stock Exchange's Nifty fell 19.80 points, or 0.40 per cent, to 4,897.60 points. Meanwhile, Hong Kong's Hang Seng was down 0.85 per cent and Japan's Nikkei shed 0.58 per cent in morning trade on Thursday, while the US Dow Jones Industrial Average ended 0.69 per cent down in Wednesday's volatile trade.