Mumbai: The Bombay Stock Exchange Sensex fell 271 points to close below the 18,000 mark as investors sold stocks, including blue-chip Reliance Industries, over concerns that surging oil prices will stoke inflation and lead to even higher interest rates. The Sensex dipped 271.06 points to close at 17,878.81 after touching the day's low of 17,849.53 with investors selling oil and gas, auto, realty and banking stocks. The gauge had lost 208.82 points yesterday after the Reserve Bank of India increased key rates for the eighth time since last March, and revised upwards the inflation forecast to 8 per cent for the fiscal ending this month, from the earlier prediction of 7 percent. Similarly, the broad-based National Stock Exchange index Nifty lost 72.95 points or 1.34 percent to 5,373.70 after hitting a low of 5,366.40 points during the session. Brokers said rising crude oil prices in the global markets due to the ongoing tensions in West Asia worried investors. However, higher closings in Asian bourses checked further losses. Besides, a significant fall in the heaviest-weighed Reliance Industries (RIL) had a bearish impact on the market sentiments. It fell 3.71 percent. The BSE oil and gas sector index suffered the most by losing 2.67 percent to 9,688.38, with RIL shares plummeting to Rs 993.15. ONGC lost 1.03 per cent to Rs 269.85. Bharat Heavy Electricals, the biggest power-equipment maker, declined 2.01 percent to Rs 1,925.65. The largest mortgage lender HDFC fell 2.57 percent to Rs 620.95. The IT sector index lost 1.36 per cent to 5,999.97 as bellwether Infosys Technologies declined 1.33 percent to Rs 2,941.55, and TCS 1.56 percent to Rs 1082.40. The auto sector index fell 2.01 percent to 8485.30 with Tata Motors, Maruti Suzuki, Mahindra and Mahindra, Bajaj Auto and Hero Honda ending lower. The metal sector index also ended in the negative zone with a fall of 0.12 percent to 15,275.23. As selling pressure picked up, the small cap index also fell 0.78 percent to 7,797.80 and the mid cap index by 0.43 percent to 6,509.68.