The BSE benchmark Sensex gained nearly 311 points in early trade today on emergence of buying by funds and retail investors at lower levels amid a firm trend in global markets. The wide-based National Stock Exchange index Nifty also moved up by 78.65 points to 5,299.10. In Asia, Hong Kong's Hang Seng Index rose by 0.21 percent, while Japan's Nikkei index was up by 1.45 per cent inthe morning trade.