The BSE Sensex extended its losses for the third consecutive session today, losing over 72 points in opening trade on sustained selling by funds amid a weakening trend on other Asian bourses.The 30-share Sensex, which has lost almost 243 points in the past two trading sessions, fell further by over 72 points, to nearly 15,655 in the first five minutes of trade today.In a similar fashion, the wide-based National Stock Exchange Nifty declined by over 19 points, to nearly 4,687.Banking, IT, metal and realty stocks led the fall.