The Sensex fell sharply by over 192 points in opening trade today. This follows foreign funds and retail investors booking profits made during the previous two sessions, taking cues from weak global markets.Profit-booking by speculators after two sessions of gains also dragged the Sensex down.The 30-share barometer, which gained over 376 points in the previous two sessions, fell to 18,417 in the first few minutes of trade today.Stocks of banking, realty, metals and auto companies suffered the most in the fresh sell-off.Similarly, the wide-based National Stock Exchange Nifty index slid by 60 points, to 5,532.In the Asian region, Hong Kong's Hang Seng index was trading 1.69 per cent lower and Japan's Nikkei shed 1.64 per cent this morning. In the US, the Dow Jones Industrial Average ended 2.22 per cent lower in Wednesday's trade.