The Bombay Stock Exchange benchmark Sensex fell below the crucial 20,000-level in the early trade today after losing over 150 points to quote at 19,974 points. Analysts said the fall in Sensex is driven by profit-booking. The 30-share barometer was trading at 20,008 down by over 116 points when reports last came in.Similarly, the wide-based National stock Exchange index Nifty also moved down by 47 points to 6,014.Meanwhile, the BSE and NSE have started 15-minute pre-open session today which is expected to reduce the quantum of volatility.In the Asian region, the Hong Kong's hang Seng index was quoting down by 0.80 per cent, while Japanese Nikkei was marginally 0.21 per cent up in the morning trade today.