India, Oct. 2 -- Market benchmark indices Sensex and Nifty extended losses for the fourth straight session on Thursday as heavy FII selling, high bond yields and a fresh spike in crude oil prices weighed on investor sentiment. The BSE Sensex dropped 570.59 points, or 0.79 per cent, to settle at 71,909.70. The 30-share benchmark shed as much as 1,187.41 points to hit a fresh 52-week low of 71,292.88 during the session. The 50-share NSE Nifty tumbled 198.50 points, or 0.88 per cent, to end at 22,421.95. From the 30 Sensex firms, Maruti, Mahindra & Mahindra, Tata Steel, Adani Ports, ITC, Power Grid, Hindustan Unilever and Eternal were the major laggards and HDFC Bank were among the winners. Foreign Institutional Investors (FIIs) offloaded eq...