Mumbai: The Bombay Stock Exchange benchmark Sensex declined by over 161 points in opening trade today as funds and retail investors locked in gains recorded in the past three sessions amid a weakening trend on other Asian bourses and heightened worries over the euro zone debt crisis. The 30-share Sensex, which gained over 463 points in the previous three sessions, fell by 161.38 points, or 0.95 per cent, to 16,772.45 in opening trade today, with capital goods and banking stocks leading the fall. In a similar fashion, the wide-based National Stock Exchange Nifty index shed 41.75 points, or 0.76 percent, to 5,042.50. Brokers said in addition to profit-booking by funds and retail investors after handsome gains recorded in the past three trading sessions, a weakening trend on other Asian bourses amid worries over the escalating debt crisis in the eurozone after the EU delayed a decision on releasing critical rescue funds to Greece dampened the trading sentiment here. In the Asian region, Hong Kong's Hang Seng index was down 2.24 percent in early trade today, while the Dow Jones Industrial Average in the US ended 0.66 percent higher in the previous session on Friday.