The Bombay Stock Exchange benchmark Sensex declined by over 190 points in opening trade on Monday as funds and retail investors locked in gains recorded in the past few sessions amid a weakening trend overseas. The 30-share Sensex, which had gained over 972 points in the previous three sessions, fell by 190 points, or 1.13 per cent, to 16,631 in opening trade on Monday. In a similar fashion, the wide-based National Stock Exchange Nifty index shed 60 points or 1.19 per cent, to 4,980.In the Asian region, the Hong Kong's Hang Seng index was down 2.22 per cent, while Japan's Nikkei shed 1.69 per cent.The Dow Jones Industrial Average in the US ended 2.20 per cent lower in the previous session on Friday.