The BSE benchmark index Sensex today gained nearly 161 points in early trade on sustained buying by funds and retailers amid a firming trend in the Asian region.The 30-share barometer added 160.74 points, or 0.87 percent, to 18,722.44 with stocks of realty, auto, banking and healthcare sectors leading the rise. The index had gained over 130 points in the previous two sessions.The wide-based National Stock Exchange index Nifty moved up by 44.85 points, or 0.79 per cent, to 5,689.90. In the Asian region, Hong Kong's Hang Seng rose by 1.02 per cent, while the Japan's Nikkei by 1.31 per cent in earlytrade today. The US Dow Jones Industrial Average ended 1.04 per cent higher on Thursday. `