Mumbai, Mar 24 (PTI) The benchmark BSE Sensex gained over 124 points in early trade today on sustained buying by funds and retailers amid a firming trend in other Asian markets.The 30-share barometer, which had gained 15.23 points in the previous two sessions, shot up by 124.18 points, or 0.57 per cent, to 21,879.50. All the sectoral indices, led by PSUs, banking and metals, were trading in the positive zone with gains up to 1.08 per cent.On similar lines, the National Stock Exchange index Nifty moved up by 33.95 points, or 0.52 per cent, to 6,528.85.Brokers said sentiments on the domestic bourses remained positive, largely on the back of a firming trend in the Asian region, despite fresh data indicating China’s manufacturing sector witnessed shrinking in March.Among other Asian markets, Hong Kong’s Hang Seng index rose by 1.03 per cent while Japan’s Nikkei gained 1.83 per cent in early trade today.