The Indian equity benchmarks extended losses on Tuesday mirroring losses in other Asian markets. The Sensex fell as much as 686 points and Nifty 50 index tumbled below its important psychological level of 17,500 dragged by losses in heavyweights like Reliance Industries, Infosys, ICICI Bank, Larsen & Toubro, State Bank of India, Bajaj Finance and Tata Steel.