The Sensex at the Bombay Stock Exchange fell by 173 points in early trade today. The fall was attributed to sustained selling by investors on renewed worries over domestic political stability and a weakening trend in global markets. The 30-share barometer had lost 239 points yesterday.The Nifty at the National Stock Exchange fell by 51 points, or 0.89 per cent, to 5,622.In the Asian region, Japan's Nikkei fell 1.71 per cent, while Hong Kong markets remained closed today. The US Dow Jones Industrial Average ended 0.76 per cent lower yesterday