Mumbai (Agencies): Sensex fell by over 31 points in opening trade on Thursday as investors locked in gains registered during the previous four sessions.

The 30-share barometer, which rallied by nearly 840 points the previous four sessions, suddenly slid by 31.16 points to 18,269.74 points in the first few minutes of trade as realty, oil and gas and capital goods stocks succumbed to profit-booking.

The National Stock Exchange Nifty index declined by 7.90 points to 5,473.80 points.

Brokers said profit-booking by market participants, following a near 4.6 per cent rise in the Sensex during the past four sessions, influenced the trading sentiment.

They also said investors were adopting a cautious approach ahead of the Union Budget for the 2011-12 financial year.

Meanwhile, Hong Kong's Hang Seng index was up by 0.17 per cent, while Japan's Nikkei gained 0.69 per cent in early trade.

The US Dow Jones Industrial Average ended 0.50 per cent higher in Wednesday's trade.