Mumbai: The Bombay Stock Exchange benchmark Sensex fell by 165 points to a nine-week low on heavy selling, mainly in realty and IT stocks, on profit earning concerns amid weak global trend. The 30-share index tumbled by 164.73 points to 17,847.24 points, a level last seen on March 21. The gauge has lost nearly 13 per cent this year. The broad-based National Stock Exchange index Nifty fell by 45.90 points to 5,348.95 points, after touching the day's low of 5,328.70. Selling pressure gathered momentum after the index-linked and largest developer DLF Ltd plunged to a two-year low on poor Q4 earnings. DLF shares lost 4.04 per cent to Rs 210.10 after the company posted 19 per cent drop Q4 net profit on higher land and construction costs. . Investors also off-loaded their positions ahead of the monthly settlement in the derivatives segment tomorrow amid reports of a weakening trend in global markets. Asian stocks declined and European stocks opened lower on deepening region's sovereign debt crisis. The index heaviest Reliance Industries fell by 0.92 per cent to Rs 906.80. The second heaviest Infosys Technologies declined by 1.76 per cent to Rs 2,795 after the company received a notice from a US court, seeking documents related to the company's use of B1 business visas. Tata Consultancy Services fell by 2.09 per cent to Rs 1,127.55 and Wipro by 0.93 per cent to Rs 435.35. The software exporters get at least 60 per cent of their sales from abroad