The Bombay Stocks Exchange benchmark Sensex opened 135 points up and touched the psychological 20,000 level in the early trade today. It was trading at 20187, up by over 220 points a short while ago. Analysts said the gain in sensex is due to fresh buying in metal, oil and gas, and IT sector stocks amid firming Asian cues. Meanwhile in Asian markets, Hong Kong's Hang Seng Index was up by 1.00 per cent, while Japan's Nikkei Index was almost flat in the morning trade. In the US, the Dow Jones Industrial Index ended 0.17 per cent up on Friday.