The BSE benchmark Sensex today breached the 20,000-mark in opening trade after two years. It gained over 100 points in early trade to touch a little higher than 20,000.The Sensex later rose by 18 points in afternoon trade to 19,926 points.The wide based National Stock exchange index the Nifty, also moved up by 8 points to 6,032. Meanwhile in the Asian region, Hong Kong's Hang Seng shed 0.26 per cent, while Japan's Nikkei was up 1.26 per cent in early trade today.