The BSE benchmark Sensex rose 133 points to trade at 18,752 in early trade today, extending gains for the fourth day in a row.Similarly, the wide-based National Stock Exchange index Nifty moved up by 26 points to 5,498.Sustained buying by funds as well as retail investors and a firming trend on other Asian bourses helped sensex gain the ground.In the Asian region, the Japan's Nikkei rose 0.37 per cent, while Hong Kong's Hang Seng gained one per cent in early trade.The US Dow Jones Industrial Average ended 0.21 per cent lower in Friday's trade.