The BSE benchmark Sensex extended gains for the fourth-straight day by rising nearly 144 points in early trade today on buying by funds and retailers amid a firming Asian trend.The 30-share barometer rose by 143.72 points, to 19,323.08 with auto, realty and oil and gas stocks leading the gains. The index had gained over 448 points in the previous three sessions.The National Stock Exchange index Nifty moved up by 40.70 points, or 0.70 per cent, to 5877.60.