The BSE benchmark Sensex extended losses for the fifth trading day in a row losing 168 points in opening trade today. IT, FMCG and healthcare sectors stocks fell on sustained selling by funds and retail investors amid a weak trend overseas. The 30-share Sensex, which lost almost 284 points in the previous four sessions, fell further by 168 points to 18,451. Similarly, the wide-based National Stock Exchange Nifty declined by 49 points to 5,618.In Asia, Hong Kong's Hang Seng index fell by1.18 per cent, while Japan's Nikkei was up 0.96 per cent in opening trade.The US Dow Jones Industrial Average tumbled 1.45 per cent to its lowest close since June 26 lower in yesterday's trade.