Mumbai: In volatile trading, the BSE benchmark Sensex on Wednesday fell 78 points on heavy selling ahead of monthly settlement of derivatives contracts and varied investor concerns ranging from high interest-rate to euro zone debt crisis.

The Sensex, which had gained 473 points in the previous session, fell 78.01 points to 16,446.02, after touching the day's high of 16,663.26 and a low of 16,363.63.

Similarly, the broad-based National Stock Exchange index Nifty fell 25.35 points to 4,945.90, after moving between 5,006.05 and 4,918.45.

Brokers said investors off-loaded positions ahead of the derivatives settlement tomorrow, and remained unsure of steps by European policymakers on resolving the debt crisis - especially in Greece.

Besides, they added, investors remain apprehensive of the Reserve Bank's high interest rate regime to tame inflation that has been impacting corporate earnings.

Globally, Asian markets were weak and the European region witnessed a firm trend.

Among the sectoral indices, IT, FMCG, healthcare, realty, tech and refinery notched up gains, while capital goods, metals, consumer durables, banks, auto and power were down.

Of the 30 index stocks, 21 declined and nine gained.

The heaviest weighed on Sensex - Reliance Industries fell by 0.11 per cent. Among others, SBI, HDFC Bank, ICICI Bank, Larsen and Toubro, BHEL, Bajaj Auto, Hero Motors, Maruti Suzuki and Tata Steel closed with heavy losses.